One problem with expelling the paint from the nozzle with the can upside down is it exhausts the propellant before all the paint is used up. Latest ones just say wipe the nozzle off after use. I've had OK success with that. I have also soaked the nozzles in paint thinner as well.

Kevin
1951 Chevy 3100 work truck
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1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car)
Busting rust since the mid-60's
If you're smart enough to take it apart, you darn well better be smart enough to put it back together.