Stickers, yes, spray paint, no. I guarantee you (with knowledge from experience) that a gas station owner (or their grumpy manager) will happily sit through hours of grainy cctv footage to find the little moment a can is visible in your hand, ignoring every other urgent task they should be handling. I wouldn't be surprised, since protecting corporations is what cops love, if some cop would then take far too much time to get the palantir/flock cameras from the local area and find your car. So unless you're just hunting these down...

A far better method would be to 'accidentally' spill some gasoline, use a napkin to wipe it up, and then 'accidentally' hold the gasoline soaked rag against the screen while fueling. Stickers, like you said, would work, because it would be harder to see you apply them.