Using a self-cleaning spray chamber for feed pellets including a dry mass flow meter operatively coupled to a hopper for feed pellet flow and a spray chamber. The spray chamber is configured so that the pellet flow leaving the dry mass flow meter strikes the side wall of the spray chamber that opposes the nozzles located within the spray chamber, thereby causing the pellets to frictionally clean the chamber side wall. This cleaning action substantially reduces the need for manually cleaning the spray chamber as the flow of pellets through the spray chamber removes the liquid additive and assists in the coating of the pellets within the spray chamber. The flow meter provides a wide, relatively thin ribbon of pellets to the wall of the spray chamber that opposes the nozzles. This provides a more even distribution of pellets for coating and better protects the sidewall from overspray coating.