Messy projects are best done with friends. Then when the kids get filthy, you can comfort yourself that 10 other kids look just as bad as your kids. You can also justify when your porch, yard, etc. gets trashed. It hasn't just been for your measly 3 or 4 kids, but 10 other kids got enjoyment, experience or educatation and that mess is really not that bad when you spread the blame out over 13 kids.
My WONDERFUL friend offered to trash her porch for my kids to make tie dye. She provided all the materials and cleaned everything up. She was even fun and gracious while we were trashing and using her stuff. I LOVE homeschool friends like that!!