I breed standard bred Rhode Island Reds. The chicks above are all females. The pullets, as you can see, at 6 weeks, have yellow combs and no red wattles forming under their beaks. I separate the cockerels from the females at 6 weeks. The difference is obvious.
This is the "bachelor pad" where all the cockerels were kept. If you click on the photo to enlarge, you'll notice all the pinking red combs forming and tiny red wattles are popping out, ever so small, under their beaks. Sexing is dead easy at 6 weeks.
All cockerels in this pen at 8 weeks. By now, the combs and wattles on the males is very prominent.
So, in summary, it doesn't take too awful long to sex them. But, you will have to feed and care for the chicks for 6 weeks until you can make the judgement. This is part of chicken keeping. It is what it is.
The only supplemental thing I have tried once was the Manna Pro supplement. It's pretty good stuff, if pricey.
99% of the time, I just feed top quality feed. I only buy from a local feed mill, they grind it fresh. It also has animal protein and a good amino acid complex. The birds simply do better, in my experience. I dislike vegetarian feeds which are now popular.
Hope that helps. There's no magic formula. Just good feed, green grass to pasture on a few hours every day, clean water and nature will take it's course. Beyond those basic things, the rest is in the genetics of the bird. Even top notch feed can not overcome genetics.