If you're working on a project and your spray can stops spraying but you can still feel extra liquid sloshing around inside, give it a quick and temporary recharge with an air compressor.
In the above video, YouTube user Chayesfss demonstrates how he uses a few short bursts of compressed air from his air compressor to recharge an aerosol can. Remove the cap to expose the stem, press the attachment down while releasing air from the compressor, and put enough pressure back into the can to get the last ounce or two of liquid out of the can.
While we'd prefer to see him using safety glasses just in case his nozzle tampering cause some of the liquid inside to expel, the overall risk is fairly minimal. He's not using a needle attachment; just a tapered nozzle roughly the size of the stem, so the chances of him actually over-pressurising and injuring himself are practically non-existent. Still if your risk aversion is strong, you can always skip the garage sorcery and head down to the hardware store to buy more cans.
Recharge Your Aerosol Spray Can [YouTube]