Get a good nylon or polyester brush for painting with latex and a good natural (animal hair) bristle brush for oil paints. Don’t use a natural-bristle brush for water-based paints like latex.

If you're applying oil-based varnish or paint, a natural-bristle (Black China, Ox-hair Blend or White China) brush may be a better choice. You can use synthetic-bristle brushes for oil-based paint ...