I had just finished my first tank using an airbrush (it went really well), and wanted to put some dirt/mud on the tracks etc.
So, I found a recipe elsewhere-
Equal amounts of:
brown acrylic paint
polyfilla ( I used Wilkes filla)
water
(It should be the consistency of toothpaste.)
I also put some grit and static grass in it, as it looked too uniform.
so, anyway, I had about half of the brown paint i needed for the mixture, but put in what i had and the mixture went the colour I wanted, so I thought it was ok.
painted (well, shovelled) it onto the side of the tank, the tracks etc. put it on really thickly and it looked brilliant.
then it dried.
and went pink!
I think due to the whitening of the polyfilla, and due to there not being enough paint in the mix.
anyway, I'll try it again, but with a LOT of paint in it next time