Pine shavings are the easiest to keep clean...and you definitely have to stay on top of it. Meaties are good at two things: Putting things into their bodies, and then eliminating things out of their bodies== a LOT of poop!
A poop board is a wonderful thing...but won't work with meat chickens (Cornish X) since they don't...can't perch. And clean shavings are a necessity for a couple of reasons, besides the smell...the added 'padding' helps prevent the broilers from getting terribly 'burned' on their breasts. Since they don't have as many feathers and spend most of their time the last 2-3 weeks plopped down on their bellies the shavings help prevent rubbing irritation. Then since they poop a LOT, the flies are attracted...keeping the poop to a minimum helps a little in lowering the fly count along with keeping the odor down.
We usually add a thin layer of shavings every day or two, and then strip their brooder, and then grow out pen, and replenish at least once a week. We also have vanilla car air fresheners hanging around (supposed to keep flies away...not 100% sold on that, but smells nicer in the coop) along with the traditional fly tape--which helps get rid of flies, but doesn't help prevent them.
We're also trying the pennies in a bag of water this summer to see if it really works as other chicken folks swear...can't hurt.
This is my dd's 6th year with the 4-H market bird project at our county fair so we have to deal with the meatie by-products every August...someday we'll figure it out!