What Brad said, we use to print nylon jackets for a trucking company and we would rub the spot to get printed with alcohol, and to make sure we remove must or all the waterproofing we would get a cup and put the jacket over the cup and push the jacket in the cup some and pour water in it. If the water drain right on thru it was good to go, then after printing we would respray that area with water proofing spray.