We paint with DD2 who is 21mos. She's probably been painting for 4-6mo now because she sees big sis do it and wants in on the fun. We use finger paints and washable paints (both crayola brand). With finger paints I take the girls outside in the driveway with either large sheets of finger paint paper or just a long strip off our easel roll. I squeeze paint out on the sheet and let them go at it. For the regular paints we have a set that comes with about 12 colors in small tubs. I pour a variety of colors out on a paper plate, give her a brush, foam brush, or piece of sponge and put her in the highchair (so she can't wander my house covered in paint). DH also took the easel outside, put the paint in muffin tins and let them go wild then just hosed them off at the end I've never had a problem with paint stains on clothes (I usually wash them within 48hrs) but I also try to either have them in pj's or older clothes JIC.
I do not have a high mess tolerance so it took me a while to get comfortable with letting the girls have paints, especially in the house, but more often than not it turns out to not be that messy.
Mom to two amazing DDs ('07 & '09) and a fur baby.
Gluten free since Nov '11 after non-celiac gluten sensitive diagnosis. Have had great improvement or total elimination of: migraines, bloating/distention, heartburn, cystic acne, canker sores, bleeding gums, eczema on elbows, dry skin and scalp, muscle cramps, PMS, hair loss, heart palpitations, fatigue. I'm amazed.