I use Tempura paints . I make sure that the kids are wearing smocks that cover the arms and front so it usually works with minimal stains.
We paint almost once a week,. I do wish there was Tempura paints in purple, pink, orange and some other colours because iI start to think that all the artwork looks the same.

I do also have Crayola paints but I find their 'washable' ones to really look dull and lifeless on the page. They aren't very vibrant and the finger paints look more like water colours once they are painted