Be very careful when using this primer. DO NOT ATTEMPT TO SAND THIS PRIMER. It will chip and peel when sanded. I have found this out the hard way. It goes on very nice and smooth. This paint would be great for small detail parts where acrylic top paint are being used, not for priming model car bodies where sanding is involved. No where on the bottle does it say do not sand.

You can put this straight through an airbrush, but you can also brush paint it if you need to. I haven't had to thin it to spray through an airbrush which is nice!

This primer is a acrylic primer. That's what the polyurethane means. This means that it's not very durable as it's grip on the plastic is weaker. Acrylic paint will not damage the primer and neither will enamel paints. Lacquers are a bit trickier as too much will melt the primer (and possibly the plastic underneath) and cause the paint to become splotchy. However, if you bump a key or something hard onto the bare primer, it will scratch. It is not very durable at all. This issue is reduced when paint is applied as the top coats will harden and help protect the kit. If you try to sand this primer, then you'll probably fail. Because it gets damaged so easily, the sandpaper will only do that more. The grey primer covers much better than the white primer and is actually smoother. This means that it sprays smoother and is probably thinner, too. Unfortunately, beyond that it's just like the white primer in quality. Which isn't that great... Just go with a Tamiya spray can primer.