I don't have clay traps either, but a potter friend of mine suggested
the method I use for clay. Each table has a bucket of water (plastic
paint buckets that cost a dollar each from a hardware store) and a big
roll of paper towels. Students wash their hands in the buckets, dry off
their hands, and then wipe the tables with the paper towels. I have
designated clay helpers who remove all the materials from the tables
when necessary.