What does the "buildup" button in the sample sub-palette which is in the brush palette do? I'm trying to figure out which one of the clay brushes fits my hard surface like sculpting style and I've read that the difference between the clay buildup brush and clay tubes brush is that button. Does it just take more into consideration the surface that you are sculpting on when turned on?

BTW, what clay brush do you think fits a polished, sharp-edged like style?