I haven't used it with an airbrush before but I can help with the other stuff.
It would probably be good to bring an extra curtain, but "PAX ruins everything" is not true. If you have Isopropyl Myristate, everything you can't scratch off can be removed through this. I have a few pieces of clothing that were almost coated in PAX and now all of them are perfectly fine. Not to say you shouldn't be careful.
For me I did not bother moisturizing before putting it on because I never needed to. I suppose it depends on your skin type. I would suggest making sure you are as clean as possible though. Wash your face before putting it on. Also warning you now: you will not be able to make very many facial expressions with PAX.
Currently working on: Hakuei Ren