According to China Glaze, you're supposed to put on one single coat and then immediately place the desired magnet over top of the varnish.. you have to do it quite quickly otherwise it will dry (on the plus side, this varnish dries ridiculously fast). I found it worked best with two coats, and that way you can make sure the first coat is shaped to your liking on your nails. If you're only interested in the colour without the magnetic effect, one coat is definitely opaque enough, and I'm not sure if this is unique to this collection, or due to the fact that I've never tried China Glaze polishes before, but their formula is awesome. It's not gloopy/thick or watery, and one coat applies perfectly sans-mess, and dries fully under a minute.
Overall, I think it's a really interesting concept that I find especially exciting since I've recently delved into the world of obsessing over nail varnishes. Anyway, if you live in Canada, the entire collection is available at the Nail Polish Canada website, and should be available at your local retailer in the US this March!