Quick tip with those cans where the propellant gas charge has been used up, but the can is otherwise still fine, and half full of the product, is to take a regular can of lighter gas ( the type you use upside down to fill a gas lighter, typically a 300ml can available for $3 from most places that sell cigarettes and Rizla papers), pull the nozzle off the can, and use one of the supplied red plastic adaptors to refill the can. Works well, you get a new charge of good R600 (propane) in the can to pressurise it, and most cans use propane as a propellant in any case. Have used it on assorted things, including expensive bottles of perfume which had had the propellant evaporate through the rubber seals with time.
Otherwise you have to get a small container, preferably one with a pop off lid, and decant the liquid into it. Pop off lid over screw type, as the liquid will gas off considerably with time, as the dissolved propellant slowly evaporates.