I have a new air brush... well, it's new-to-me... and I want to spray a primer base on my model.

I've heard for airbrushing you can just spray the can paint/primer into the jar for the airbrush and spray it.

Does that really work? Or should I thin it? If so, how much and with what is it best to thin it?

While I have never tried it with Primer, there is no reason it wouldn't work the same as with other spray can paints.

Biggest thing, once you get the paint sprayed into your airbrush bottle is to let it sit for 30-60 mins before putting a cover on it, or using it.

Reason for this is even though you have decanted the paint into a bottle, the paint still contains some of the propellent in the spray can, and jarring the bottle can cause the propellent to react and release its energy and in the process making paint fly all over the place, so you let it sit for a bit, and allow the propellent gases to bleed off naturally.

As far as thinning the primer...as I said, I am not sure about that, should be able to tell just by looking at it. I would hesitate to thin it any, unless it looks extremely thick, I would be more apt to up your airbrush pressure another 5-10lbs to spray it instead.

Thanks Scott!

I would never have thought of the propellant and needing to let it sit for a while.

The primer does look rather thick, compared to the "consistency of milk" I've been reading about elsewhere. I'll see how it goes on a test piece first, but I'm thinking increasing the air pressure like you suggested.