No, not slow feathering vs fast feathering.hard feathered as in fast growing feathers and soft feathered as in slow growing feathers? That is a sexlinked factor, symbol K. Slow growth is dominant
Some breeds have "hard" feathering genes like Aseels where the feathers lay tight against the body and are stiff.
Others are soft feathered breeds like Orpingtons, where the feathers have volume and are soft.