What do I use for a wash?

A wash is used to generally bring out the low laying details ie. panel lines, around rivets and bolts. It aids in adding depth to the model.

Apart from soap and water :-) there is a good thread in the painting issues forum that i found very helpfull.

linkname https://armorama.kitmaker.net/forums/262&page=1

In my opinion, the best medium for washes is artist's oil paint. Enamels also work well. In either case, make sure you seal the paint first with several clearcoats or the thinner in the wash will destroy the paint. I use acrylics for my paint layers and clearcoat, then wash and drybrush with oils.
I've also heard of people using acrylics for washing, but I haven't tried that so I can't comment.

I usually use black or brown artist oils thinned with turpenoid. I don't have any trouble with this mixture damaging the underlying finish.

Patrick

I, too, generally use artist oils or enamels. I have not tried acrylics. Just use a little bit of paint no matter what. It's supposed to be tinted thinner not thinned paint. You can always add an add'l wash if you did not get the effect that you were looking for.

I have read quite a bit about modelers sealing acrylic or enamel paints before applying the wash. I have never had any problem with the undercoat lifting. As a rule, I will let the undercoats fully cure for 3 days before applying the wash.