I use egg cartons for the tempera paint trays,
and long cotton swabs I got from the nurse (or medical supply store) for the brushes.
Poke holes in the carton to hold the swabs so they are not standing in the paint.
Store the paint egg cartons in large zip lock bags.
I got this foam head at a beauty supply store and I let the kids put the swabs in it at the end of class....quietest table first! They think Pine Head is the greatest thing.