I think I need a method of using the rest of the paint from partially used cans
I think I remember
@BartRidesEternal was using the last of his cans, he might have suggestions. I found a great set of instructions in another forum:
https://www.hobbytalk.com/threads/removing-paint-from-aerosol-cans.245786/
"Remove the spray button from the can.
Shake the can to thoroughly mix its contents.
Set the can down on a flat surface.
Using a file sharpen a small nail to a point and with a small hammer gently tap a pin hole just inside the lip at the top of the can.
A pinhole is all you need.
Just barely break the skin of the can.
Allow the pressure to fully escape, about 15 minutes.
Now similarly tap another pinhole opposite from the first on the other side of where the spray button was.
When all pressure has escaped enlarge both holes with a larger nail or phillips screwdriver.
These two holes will equalize the air pressure in the can so you may pour out the contents.
Now you need a suitable container to hold the contents.
You may use any soft plastic container i.e., polyethylene not hard styrene.
I choose either Ketchup bottles or Barbecue Sauce bottles.
Yeah, I do a lot of Barbecuing around here.
These bottles are constructed of soft vinyl like plastic which will not react with the chemicals in Enamel or Lacquer paints.
They also come with the benefit of having a small mouth opening so you may safely pour your thinned paint directly into your AirBrush Cup.
Gently pour the contents of the can into your new container and leave it open for about 4 hours.
Return every so often to swirl around the contents assuring that the gases get released.
The paint still contains propellant in liquid form and will create pressure in your new container if shaken.
Diluting it with the prescribed amount, 35%, of Paint Thinner will deactivate some of this tendency to bubble up and boil over.
I screw on the cap, gently shake the bottle and very easily loosen the cap 4 or 5 times repeatedly to allow all remaining propellant to escape."
There's also a method there for transferring paint from the can when you still have propellant function