Does anyone have any preferences when spraypainting foamies. what type of paint works best. I've heard Rustolium works well, but i dont want to use it and have my kit dissolve before my eyes, ya know. Any suggestions?

Krylon Fusion works really well. It's made for plastic and won't eat up foam

Has anyone ever used ink for painting foamies?

It's already really thin, almost like water, and dries fairly quickly. I have black india ink that won't wick through the foam, so stencils and stuff will keep the lines sharp.

Plus, it works well with airbrushes, recommended for practice

Dip pen ink comes in a couple colors, mostly basics, but anyone ever tried?

never even thought of trying that.

Personally I use Krylon Short Cuts, I think it's a similar formulation to the Fusion. I've painted about a dozen foamies and never had a problem. I like it because the cans are smaller and cheaper, kind of a silly reason, but it allowed me to buy every color they have.

When I rarely have a foamie, I just use Tamiya colors, and air brush the stuff on.

Krylon H2O paint from a craft store, brilliant colors when put on white foam

Rust-o-leum "Aqua" range of water based spay paint. Tamiya "TS" range of aerosol spay. work well.

krylon shortcuts or krylon H2O works great

FOR DEPRON OR BLUCORE USING SPRAY CANS

Krylon 'H2O' gives the brightest colors out there!!! And with no melting, no matter how heavy you spray it on! But it lays on a little heavier then most others. 2nd choice would be Krylon 'short cuts'. It does a great job.
As for airbrushing I dont know, but I would sure like to have one!

Heres a few pics of how bright H2o paints are. The Tensor is depron, and the Judge edge is blucore.

I have been using the acrylic hobby paint from the craft section at Wal-Mart. They are really really cheap ($0.44-$0.79 per bottle) and come in tons of colors. Pretty easy to spray with an airbrush too.