I've Alsa's Mirrachrome with an HVLP gun as well as an airbrush. I have yet to try any of their Killer Kans, but if the Kans work as advertised, they're worth the cash.
The first project I tried with this paint was my Jango Fett helmet. I used it as a base to get a proper metallic finish before adding the trim colors. It turned out to be a bit too shiny and I actually had to dull it down by messing up the clearcoat on purpose:
The next project was the pair of my Warhammer 40K Space Marine helmets I painted up. Again, I used it as a metallic base before adding finish colors and battle damage. It was a bit of a heartbreaker to cover up this finish:
Along the way I fell so completely in love with the product I decided to repaint my car:
With the car I got the worst results I've ever had, but I learned more about this paint than with any other project I've used it for before or since. First off: yes, you have to follow the directions. Second: surface prep is key. Not only do you need an absolutely perfect gloss finish underneath the chrome layer, you need to make sure there are no fingerprints or oily residues of any kind left behind. Finally: the paint will hold up to a bit of handling without a clearcoat on top of it. Still, if you want it to last for any real length of time, let the chrome layer cure in a warm, dry environment for as long as you can before you apply the clearcoat over it. If you do it right, this paint will hold up just as well as any other high-end automotive finish.
I've found cheaper versions of chrome paint, but so far I have yet to find a version that looks as convincing. I like their products enough that when I get to talking about them people tend to ask me if I work for the company.