Ah yes, the coolest thing since sliced bread! Well, if you are using acrylics or your final base coat is acrylic, than you would use a extremely diluted mixture of spirits\thinner and say raw umber or black\browns. If your final base coat is enamel, use a diluted mix of the acrylic paint and acrylic thinner (Tamiya, alcohol ect) Remember that opposets don't eat each other. The goal is to have a watery mix-dam close to clear! and let it flow into the panel lines and rivets, ect. You could also purchase pro modeller weathering wash and just start with it. Once you've coated the model or part, let dry and wipe off the excess, Remember to ALWAYS use the opposite paint and thinners on the final coat of paint or else you'll wipe away the paint job instantly! Acrylic thinner won't eat enamel and white or mineral spirits won't harm acrylics. Check out my new post from today, second to last pictures and you can see what a wash will do. Its just a blob of black paint and a few drops of thinner. Take care and post pics! http://www.scale-models.co.uk/planes/6738-new-build-il2-sturmovik1-48-a.html#post45229