i mix it 50 - 50 with cellulose thinners then airbrush it. i used the whole bottle on this car to get the colour i wanted, but usually i only use half the bottle.
i agree that the car is junk, i hated the kit that much i couldn't be bothered with fixing it, so i used it as a wee test car for trying to get rain drops with my clear coat, but didn't go to plan.
I used Gloss Black Paint, then i coated it with Tamiya PS53 Lame Flake, then a wee bit of clear coat. The bonnet is painted Black from the late 90's McLaren, so it has a wee hint of silver flakes to it.