It's not expected for the end user to work in a hospital-sterile environment when installing GunSkins, but the cleaner the area, gun, and hands are the better. While working with the vinyl it may be possible for sweat and skin oils to get on the adhesive from your hands. This is especially so when grabbing the material to stretch it into place. This contamination reduces the ultimate adhesion level of the backing.
It is advised to wash your hands and even wipe them with a cloth using isopropyl alcohol to remove any remaining moisture, oil, and debris to reduce the possibility of contamination. Another alternative is to wear a pair of forming fitting latex or vinyl gloves. A simple solution like this can go a long way in ensuring the success of your GunSkins installation.