I have twenty year old cans that spray. Invert the can until air sprays, clean the nozzle, store cool and dark, pick-up and shake one when getting another too. Clearing the tubes are less of a waste than a clogged can.
A drop or two of thinner in a can outlet and repeated presses once nozzle is on will sometimes unclog a can seal or nozzle. So will an increase in can temp. (pressure rises) and sometimes rigging the nozzle down/open allows can solvent to weaken/dissolve the set paint.
