What are brushes called scrumblers?
Although sometimes referred to as scrumblers, I believe the brush you are referring to is a natural bristle round usually known as a ‘Scumbler’ after the haphazard technique of moving paint around on the surface. This is often done with thick paint or applied in layers, putting a lighter color over a darker color so the darker color shows through in varying amounts and can create texture and depth in a painting. A scumbler brush has a broad, round point as opposed to a fine point.