I typically use Taom chalk at home, but tend to use Master chalk if that's what is avail at local pool hall or friend's house. When I make that switch, I'll scuff the tip a bit to remove excess old chalk and then apply the new stuff pretty thoroughly. So - opinions on switching back-and-forth? If this is an ok practice, is the scuffing necessary? Or better to just apply the new chalk on top of the old?