Vicki, I knew if I searched long enough I'd find it, another reason to organize my Favorites!
I always wanted to try this and I don't see why it wouldn't work with the 5 gallon buckets. They used black nursery pots here, added pipe insulation to form a rolled rim and painted them.
http://www.gardengatenotes.com... At the very least you'd have to prime the pots with a bonding primer. I get mine at Sherwin Williams and have them tint it gray because most of the colors I choose are dark to paint plastic containers. Krylon Fusion should work real well but it could tend to be expensive if you want really good coverage. Make sure to show us what you decide to do with your buckets!