Don't much fancy airbrushing GW washes. I don't think my wallet could take it...
Tamiya clear should be ok, but be aware it does weird things if you thin it with water. Tamiya thinner, otoh, is peachy.
Incidentally, zenithal highlighting like that is exactly how I did all my chaos marines and daemons. You don't need to use the transparent colours (altho there's nowt wrong with it.) You can just use 3 tones of the color you want to end up with. Going grey first allows you to use the black undercoat as tone 1, mind you. I used a Tamiya dark green spray, iirc, then airbrushed on a lighter green then a kinda beige colour. I thiiiink I may also have given them a greenish red wash afterwards too, but whatever. The principle is sound
