Line breeding or In breeding is not meant for production of numbers. it is for the development of traits. It goes hand in hand that you would select the best of the traits you see need to be increased. In fact it actually takes a considerable selection pressure to get increases even with such intense breeding. It is considered that a selection pressure of 50% or less actually causes you to loose ground. An example of what selection pressure would be. Say you select only 1 out of every 100 males to use as a breeder. this is a 99% selection pressure, but only on the males side of the blood line. if you take this male and then breed them with all the females from that generation, this creates a 0% selection on the female side of the bloodline and is actually a 50% selection pressure on the line as a whole. which is considered loosing ground. So you need to also apply selection pressure on the females as well. True selection pressures of 95% or more can and will result in dramatic results in improvement of traits selected for. Chickens happen to be very responsive to selective breeding with measurable results in just a few generations. Selection works best when only a few traits are selected for as the more traits you include the lower you need to take the selection pressure so that any individuals can even qualify. for example yo may be selecting for feather color and pattern as well as temperament. it is far less likely you will find improvement in all three traits in one bird but it will be more common to find improvement in two of the three, and even more common to find improvement in just one trait. breeding different lines for each separate trait and then breeding those lines together is often more effective than trying to increase to many traits in one line. I see the rotational line breeding system described in the link from the OP would work pretty well with that. say each coop is selected for a single trait, two at most. those selected traits would then be carried to the next coop as the Males rotate. Keeping some expression of that trait showing in all the coops with time. For example increasing the temperament of all your birds as the better mannered roos rotate, etc. of course females need to be just as seriously selected for the traits of there coop, this way always increasing those traits with every generation from that coop. Line breeding is useless if you do not also exert considerable selection pressure.
