What solution do you use for spray gun?

You can use any liquid solution you chose for your skin. It can be vitamin c, liquid peptides, oxygen liquid to mist on the skin. It you want to use just water it has to be distilled.

How to switch from micro to oxygen? Or from oxygen to micro? Because they both working together.

Hi, To switch from the microdermabrasion to the oxygen injection function, you need to remove the microdermabrasion tube and use it again. They do not work together and need to be used separately.

can you use the spray gun for airbrush makeup?

Yes but it’s attach to the machine

Machine is starting and stoping I just got it today . What to do?

If it is the oxygen handle your using, that’s what it does. As far as I could tell with the micro dermabrasion handle, the sound stayed consistent. I wouldn’t pay attention to the sound but make sure that either the suction on the micro dermabrasion handle or the pressure and the oxygen gun is consistent. The machine sound isn’t necessarily congruent with the function of the gun or handle I have noticed