Spray paint gas simulation How would you simulate the paint sprayed by a spraypaint can? It should be animated as hitting a wall covered by a stencil, so it must have some kind of gas-dispersion effect when it collides against the stencil and the wall. I'm working in Cycles, and paint colour is black.

I mean not simulating the paint getting sticked to the wall (that can be made with dynamic paint) but the paint flying through the space in between the spraycan and the wall. That's why I ask about particles system and not dynamic paint.

Would a smoke simulation solve the issue?
I would use both a smoke sim and a particles sim. 

You can use a smoke sim on the actual particle system. This is what I did here.

I used the particle system for the little tiny paint drops and of course the smoke for the mist.  






Create a circle with a face (as the nozzle for spray)
Create an icosphere to use for the Particles.
Add a particle system to your circle
Make sure you choose your icosphere as the object to emit. 
Create a big box for your Smoke sim, make sure it covers as much as you need reach the stencil and wall. 
Add a wind Force Field in the direction you want your paint to blow.
Make sure your wall is set as a collision object and have it set as a Canvas for dynamic paint.
Choose your circle emitter and make sure you choose for the smoke to emit from the particles. I have a screen shot below how I set it up. You will obviously need to change the settings to better match your scene but that is the gist of it.