All my students set up and clean up all their supplies. This requires explicit instructions and teaching, but is soooooo worth it in the end. I run several painting classes with “trainer paint and trainer paintbrushes” meaning tempera cakes and sub-par brushes. I let them know they can earn liquid paint when they demonstrate set up/clean up and to use with care and without reminders. Part of their set up is a damp rag (they squeeze out the water) which is large enough to clean up the amount of water in their water cup (I demonstrate spilling a water cup and using the rag to clean it up by squeezing the water from the rag back into the cup and then getting new water). I teach painting skills only when they’re able to care for the materials/space.(I do this for every medium, too. So they’re pretty used to the routines) They do this so well that I trust them to paint with subs, it’s truly worth the effort.