I've been trying to find specifics on how to optimize breeding but have not had the greatest luck. There are a lot of factors: How many birds you start out with, How related they were in the first place, Which ones you pick to breed together and How long you keeping going until you add something new. I would think most backyard breeder don't bother with the details, let their bird breed to whoever(culling obvious weak one) then add a bird every few generations or until too much of the stock starts showing weakness. You can even breed to semi related lines then when you need new blood use those birds(start with the same foundations but don't mix the line after that). Ever option has good and bad points about it.
Might help its for rabbits but the way you line breed seems to work same for most animals only different is when you add something new: