I put future over them with no problem. My one big complaint is that they can solidify/dry out a bit. They are almost like a very dry grease paint for the model that you drybrush. Some colors are soft and transfer well, others are hard and you have to really get into them, so practice with them. Also, unless you want the colors mixed, get some eyeshadow brushes at your local target/walmart/etc. in the cosmetics aisle.
I read somewhere online that if you make a mistake you can clean them up with water and start over, but haven't tried myself.
Groot