The spray emitted from an aerosol container is normally produced using what’s called a particle system. This animation technique would be appropriate for the droplets.
Depending on the amount of realism you wish to achieve, you can composite this droplet particle-system with others whose materials produce the “gaseous” look caused by the droplets that are so fine you can’t see them. Compositing also can help the spray look thicker.
All of these layers would be built on top of the model of the can itself, and layers which represent whatever hand/finger there might be, pressing on the button. The button itself, as it moves in the act of being pressed, might be a composite layer too.
Sandwich all these layers together and you’ve got a marvelous spray-can.
I think it would be very difficult to try to “do it all at once,” in a single render, and of course it would be expensive. The complex motions of an aerosol spray-jet would be easily described as layers of motion.