If you are going to empty an overfilled canister the result will look like this:
Since you know that this will look like this and since you know that your clothing afterwards will be spilled with a toxic soup which is stinking like the hell you will not even dream to do that. You will prefer to put the canister anywhere where nobody will find it.
Is there really no solution??
Look for a spray bottle - and old spray-bottle is best, but be sure that the bottle is still in a good condition. (Tubing must fit tightly! Look for a bottle which needs much power to be compressed.) Now take a pair of scissors and cut of the end of the outlet pipe!
Pull out the outlet pipe and insert it now with the short part into the bottle:
The following video shows, how to use this construction. Consider that the movy speed is enhanced twice to keep the size of the file low.
As the video shows, compresse the bottle as much as possible and the insert the outlet pipe into the canister. When the bottle expands to its original volume it sucks the content out of the canister.
When you now unscrew the cap you will have a bottle which is about half filled. OK, and how to empty an half filled bottle needs not to be explained here...
Probably you are not familar with the thread of the canister but this is a standard size. If you measure the diameter, you can buy a suitable nozzle:
The nozzle has a lever on the back side to switch between "open" and "closed". It is cheap and it is best to have it at hand preventatively so that a trouble will not at all become a trouble.