You might look on this Forum for what folks have had success with in the past. A lot of folks have tried to breed dual purpose for meat, or to create "meat mutts", hatchery birds or mix birds with better meat production. There's a number of ways to start. Personally, I'd recommend not doing a...
Where do you plan to source your chickens from? Most large commercial hatcheries optimize their breeds for egg production, regardless of their original purposes
Since you want to breed for meat, is there a reason you're not starting with a dual purpose breed already optimized for meat? Check...