No pressure Andy; I mean don't put any pressure on the clay, just the weight of your hand is enough, if there is a really stubborn particle stuck on the paint like an iron fileing, it may actually mark the clay with a slice, don't press to make it work just go with lots of passes and in different directions. Straight lines yes but following the panel, go over lenses, badges, glass and even shiney plastics... You can pinch the clay to a point to get into those annoying holes in scripts and around the side repeaters etc.