I've got both stencil painted and stickered (non-die cut, from Walmart). The paint actually seems to scratch off faster than the stickers, and looks crappy. Is there a process other than just spraying on the paint?
Never had a problem with any paint coming off. Are you using painted or shot blasted tanks? All of mine are shot blasted (or whatever the term is for bare tanks). I would expect it to be easier to take off of painted tanks. It may also be a matter of the paint you use but I doubt it. I usually just grab one of the better brands that is designed for use on metal and use the flat stuff.