Hiya fluffho!
I can't say much about marbling cos I don't do it but I do know that normal nail polish is used. The best person to ask is Laystar and I know Glorsclaws has had some fab results lately too.
For any nail art, I use acrylic paint which is water based. For free-hand, I just add a drop of pain onto a saucer and paint away with fine brushes. For air-brush, I use the same paint - a couple of drops into the airbrush and away I go. The paint I use is mainly Createx but there are other great ones on the market.
I always use a base coat before I paint and because acyrlic paints are water-based, they wash off so it's important to top coat with a suitable one. I always use an airbrush top-coat - [if you don't use the right top-coat with airbrushed art, it can crack and look like an old oil painting].
There is a thread somewhere about mobile-phone airbrushing cos I asked a long time ago and Ruth [Nailsinlondon1] very kindly gave me fab instructions and I airbrushed a lovely phone for my mum at Xmas so do a search and you should probably find it.
Lastly, I personally don't think I'd want to have acrylic on my toes [mainly cos I can't bend down that far to do them]!! :lol: :cry: :lol: but I would have gel on them. I intend to offer it as a service later as I have just bought the Brisa kit.
Anyway, hope this has helped.
TTFN
Carol