Aha, what you've got will work. Depending on how many you're hatching I'd think about putting the female offspring of the polish with the male offspring of the cochin (amd vice versa) and only keeping the silkie feathered chicks (about 25%) as that way you won't have to worry abut who carries the silkie feathered gene. Keep all female offspring of the pure silkies though and keep crossing back to the pure silkies with each generation of roosters. I'd only use your Polish and Cochin Roosters for the initial generation, and keep the best cockerel (or maybe 2) from them, but then replace them with their sons and so on til you're back to a higher percentage silkie. I would love to see what you get so please post pics of your progress! I will probably have some cochin x silkie chicks hatch at the end of Jan (its summer in Aus), but this is mostly as I cannot tell the pekin (bantam cochin) and silkie eggs apart well, i'm hoping to just keep the pures but i think the pekin silkie cross is cute.