Systems, methods, and apparatus for simulating natural media painting in a digital painting application (or painting simulation module) using a two-layer model of a virtual paint brush may more accurately simulate real world painting techniques than conventional painting simulations. A two-layer brush model may include a reservoir buffer and a pickup buffer to separately represent the paint stored in the belly of a paint brush tip and paint that has been picked up on the surface of the brush tip during a brush stoke, respectively. The two-layer brush model may also include methods that automatically control how virtual paint moves between these layers and a digital canvas. In simulations that employ this two-layer brush model, virtual paint may be deposited on the digital canvas directly from both of the buffers. The amount of paint deposited from each buffer (and/or the ratio of the amounts) may be configurable by a user.