I like to use cardboard scrapers to clean off the surface of a plaster
wedging board. I save the "drop-out" from work matted for competition and
cut them into 3x5-ish pieces. There is a huge stack of the in a box next
to my wedging board for clean up. Use them once and pitch 'em.
Cardboard scrapers are good for applying gesso and for short runs with silk
screen printing.
Christa