If you were really safe, you could get one of those sports inhaler..thingy..yeah.
Basically is a mask that you put on, and attach a small tube to it filled with pure oxygen. A bit like a divers oxygen setup, but a hell of a lot smaller. well, it fits in your hand.
They're £30 over here, and you can get them at argos
Personally though, Ive never used a mask for sanding or spraying. I just used a rag or my top. For fiberglassing I've used a very simple mask.
Probably why I have asthma
The spray leaves you a little dizzy when your in a small room though
Take care all,
-D.