I have tried various thinning potions, including alcohol, windscreen cleaning fluid, etc. but I have found that Tamiya acrylic thinner works great with their acrylic paints. The large plastic bottle lasts ages and most importantly, it works. With Tamiya acrylics one MUST not brush paint over bare plastic. Prime it or paint it first. When I don't prime, I lay on two or three thinned coats of paint, letting each dry between. That's the key I think. The first coat or two will be "streaky" and uneven in places. Sometimes this is a neat effect and you can leave it as is, or add a darker or lighter shade to the next coat and enhance that a bit. Keep it up, letting each coat dry before applying the next. Doesn't take
long with acrylic paint.
Later you can slop on a thin acrylic wash in a darker shade to give it some tonal variation. You probably can't apply too many washes, especially for dark colors like wood or leather. I like to experiment with brush and airbrush.
