Glad to hear you're trying out the broiler project for 4-H! Sorry you haven't heard back from anyone yet, but thought I'd share some of the stuff we learned over the past few years. My daughter had a market broiler project for 5-6 years, last year she didn't due to Ohio's restriction on poultry shows/gatherings and potential for bird flu.
I know you will get lots of different advice, you'll just need to sort through it all, read everything you can and find out what works best for you.
Our 4-H club did have a pretty experienced family with poultry so that was great. Then our county (I think the whole state) requires every 4-H member who had a market project of any type (sheep-poultry-beef-hogs-goats,-rabbits,etc.) to attend the Quality Assurance program--that was required every year, it reviewed all of the major things needed for raising any project for human consumption. Very helpful. Then our county would hold a clinic at the fairgrounds with some really knowledgeable folks leading it...plus our local feedstore would do the same, so there were local resources out there. Make sure you check locally as your state may have different requirements for your project.
Our county required a market pen of three--the goal was to have matched trio weight and carcass-wise, with a minimum and maximum weight limit they would have to be within, it wasn't based on just having the biggest birds but rather the best matched trio with the "right" meat proportion, determined at the fair by the judges.
We would order 15-20 chicks (10 the first year--the more you have the better your chances are of getting a matched group, plus you may lose some before fair time), in mid June, they arrive mid-July and the fair was exactly 8 weeks after. Everyone got their chicks from the same supplier, picked them up on the same day from the same place--level playing field that way. It was interesting to see what showed up at the fair as the sizes were pretty varied depending upon the care and food that had been given. You could tell those who were in it just to sell them after the judging at the auction.
We kept the chicks in a large brooder (4'x4') under light for about the first 4 weeks. They had free access to fresh water (with electrolytes the first couple of days), and free access to medicated chick starter. Then we would rig up a large run for them,the last two years it was in our main coop outside of the laying hens area. I made a 'fence' of sorts out of pvc poles and some wire--it was about one foot high and 8 feet long--they can't jump over it. It was August by then, they still had the lamp if needed but they did grow some feathers and it was warm. Our bigger problem was the heat--we'd run a fan if they acted like they were too warm--heat can easily kill them. One thing that was really helpful to know was we made sure the water was on bricks at one end and the feeder was at the opposite end on a raised platform (about the height of a pallet, 4-5" high). The reason is, these franken-chickens would be content to lay in one place, never moving, eating, drinking, pooping and never getting up. You want to encourage/make them move around to build up muscle--they are judged on that. You just have to make it so they can get up and down--like I said, they don't fly...or hop...can't be too high, don't want them falling off either, especially the last couple of weeks when they are huge and clumsy.
After we ran out of the chick starter we switched to Purina Honor Show Chow. No, it's not the cheapest feed out there, but it's pretty important that you feed them the highest quality feed you can to produce the show quality birds. I'm not a Purina rep...just know that I have seen the final result of meat chickens that were not fed properly for the 8 weeks they had to prepare for the fair. Go to your local feed store and see if there's someone there who can help you. If you're raising meat birds for yourself then feed them whatever you like, won't matter if they aren't "show/market" quality, but don't cut corners for a show project, especially your first year. Experiment the next year once you have a feel for the process. That's just my opinion though :)
The other thing is, we never withheld feed--I've read about the feed 12 hours then withhold 12 hours, or feed morning and late day but that never worked for us. They would gorge themselves when feeder was refilled, coughing and choking. We figured they were not eating from sunset to sunrise (9am-7am) so they weren't eating anyways, and they'd wake up starving. Less stressful for them. That's about it except we would use large plastic wire ties on their legs, different colors for each bird, then note the colors on a clipboard. Then we'd rig up a scale by using a hanging scale (cheap from Meijer), tying it to a screw-eye in the doorway of the coop. Then we took a 5 gallon bucket (weighing it first to subtract it's weight from chickens weight) and put each chicken in the bucket, one of us did the chicken wrangling while the other (me) sat and recorded the weight for each color. Make sure the tie is loose on the bird, their legs end up huge! We would also rank them by feeling along the breastbone, you want the breastmeat to be more of a rectangle than a heart shape from breast to between legs--you don't want a 'point' between the legs (picture a heart with the pointy part being between the legs...not good. Want even meat development. Also want meaty drumsticks. We'd rank them 1-5 at about week 6, then again a week later, narrowing down to the top 4-5. Then a couple days before fair make the final picks for the best matched trio. We separated the top picks from the rest then, no need to risk them getting hurt by the tanks trundling around :) The rest went out into a covered dog kennel with shelter.
Fair day we'd bathe them--use baby shampoo and warm water in a large bucket or mudroom sink. You need to work the yucky stuff out and get them as clean as possible--appearance and care is part of 4-H judging. Then do a rinse with some white vinegar in it--removes soap residue. Have a large clean towel ready and after rinsing, wrap the bird up snuggly==make a chicken taco. They won't fight it--quite pleasant experience for them. We've even blow dried them to speed up the process--they loved it. Plan on one more bath before the sale but you won't be able to do as thorough of a job as you will at home...a buyer wants to see a clean, healthy bird with a confident, prepared handler.
Finally--if you know of folks who support the fair absolutely contact them a couple of weeks before and thank them in advance for supporting 4-H. Any family, friends or folks involved in youth support or livestock (such as feed dealers,etc.), let them know you will be tackling this challenge and would really appreciate their support. The once sale night arrives, regardless whether you win the class or end up dead last, if you've done the best job you could and have clean, healthy market birds, smile and enjoy it--it is a lot of work the last couple of weeks, but you won't regret it a bit. My daughter placed in the top five the first 3 years (with 50-60 entries) and the 4th year was grand champion out of 63 entries...that was a good year :) Her last year she ended up in 6-7th place out of 50+ so not in the ribbons, but she was fine with it...hadn't put as much work into it by then.
I hope this helps you a bit, I tried to cover a bit of everything--keep doing your research and best of luck!
The birds who didn't make it to the fair :)