Abstract: A hand-manipulated rotary brush mechanism employs flywheel gear means and associated gear assembly means to provide rotary motion for brush applicator means, said flywheel gear means providing suitable blade means thereon which are projected into the flow path of a continuous fluid flow stream as channeled through the rotary brush mechanism, and said flywheel gear means being larger and heavier than and combined with the associated gear assembly means which directly supply the rotary motion of the brush applicator for the purpose of providing opposition against and moderation through inertia of movement of any fluctuation of rotational speed of the brush applicator.