TOGWT

Usually if the spray stops working I soak it in semi-hot water and it generally releases the blockage.

I've never tried applying that much protector at one time...can't answer your question

Zurichgnome

I asked a paint store guy how I could avoid wasting 90% of the spray paint cans due to plugging of the nozzle. First he explained that the paint companies have absolutely no incentive to fix the problem -- like like the light bulb makers do not really want long-life bulbs. So don't expect it to change anytime soon.

The trick, he said, after you are done with your project, turn the can upside down and spray it that way for about 5 seconds. Didn't get into the physics and/or propellent issue behind this, so I can't tell you why -- but I haven't had an issue since.

aviography

That's the standard trick as inverting the can leaves the pick up tube pointing up where there is no paint, spraying at that point forces straight propellent through the pick up tube to clear out the nozzle so it's free of any remaining paint to dry out and get clogged.