Cheap Decorating Brush

A cheap decorating brush is useful for applying gesso or primer to a canvas because you don't have to worry about getting it spectacularly clean afterwards, which can be quite time consuming. (And any primer left in the brush will cement the bristles together rather well when it dries.) The disadvantage is that hairs tend to fall out of a cheap brush; either pick these out with your fingers or a pair of tweezers.