@Scott.....

You can use distilled water, it just performs better with either their thinner, airbrush cleaner, or windex.

Ask Chung, he has been using Windex to thin his Vallejo, I believe about 10:1 Windex to Paint to start and adjusting as necessary from there. Just plain blue windex.

Here is another....friend here in Fredericton, has actually been using Future, 2:1 with the Vallejo paint, splash of Vallejo thinner and says it works great. Might have to give it a try.

As far as their varnish, no, don't need to thin it. Doesn't matter if you have the Model Color, or the Model Air Varnish...same stuff, just a different label. If you do want to thin it....just a couple of drops would be all you need, as it is pretty much good to go out of the bottle.

@Chief...........

Depends on what you are using to thin them with. I assume if you had the RLM Box, that they were the Model Air colors?. I can't say I have ever had a problem with the paint drying (either the Model Air or Model Color) in the airbrush, or drying too fast for that matter.

I don't clean the airbrush with water, you generally need something a little stronger, their airbrush cleaner is recommended. I don't know about them drying in the airbrush rock hard. With the airbrush cleaner I have cleaned very easily paint that was dried on for days, came off no problem.

Tamiya PS-55 I believe is designed for spraying on Lexan RC bodies.

Quote from Tamiya's website:

It is supposed to go on the outside of a Lexan body (where as normally they are painted from the inside) so I would venture a guess that the PS55 would likely lift most paint, as it is not designed to go over paint, but the outside of a Lexan body.

Also depends on how long your paint has cured, with Vallejo no less than 24hrs to be cured depending on your atmospheric conditions. Longer if it is humid.