Hi
Actually you can use pretty much anything to do a wash, assuming that what you mean by wash is actually a very very thinned paint
(or "colored thinner", as some guys like to call it
).
- Pigments (like MIG) can be thinned with water or turpentine (or any equivalent), but since they are very coarse in nature,
the final result is not very good in most of cases. That's why most of the people do not use them for this purpose.
- Painting Oils are the most used media. Thinned with the appropriate thinner (either the classic turpentine, or the more modern ones,
less toxic and without any smell), they give you the best results, because they are very forgiving, due to their long drying times.
Thatīs my favorite method.
Recently have appeared on the market some types of oils than can be mixed and thinned with water (for persons who are sensitive
or allergic to the oil thinners used), but I tried them once and did not like them.
- In place of oils, you can you also enamel paints. The method and results are similar to oils.
- Acrylics are also OK. But since they dry fast, and once dried there is no easy way back to remove them, you have to be fast an assertive
in order not to have any regrets later on :)
Personally I have done it, in very rare cases.
- Writing ink (ink used in calligraphy) can also be used.
I do not have experience with them, so cannot give any tip.
One final word of warning:
If you have painted you model with acrylics, there is no problem with any of the above methods described
but you have painted them with enamels, please be careful, because the thinner used might dissolve the enamel.
In that case, protect the paint with a good layer of clear acrylic varnish, before applying the wash.
I hope this is of any help!
Cheers
Antonio