Andras - not sure about the one you saw, but lots of people here use Bare Metal Foil. It is a thin foil with an adhesive already on it. It is about $6 a sheet. Personally I've only used it to mask canopies for aircraft but several people have posted pics of builds of say a P-51 done entirely in it and it looks fantastic! I know it does require some getting used to to come out right.
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Bare MEtal Foil is specifically for plastic models, you get it at the hobby shop
The buffing compounds I am not sure, are you referring to the ones for wood and ceramics? I'm not sure what kind of finish they would leave on plastic but you could probably try it on an old kit or buy a cheapy kit just to try it on.. I would think it wouldn't adhere wll to the plastic (or stay on long) but I've never tried it so who knows?
What I use for a BMF look is Alclad II, it really does look like metal when you are done, here is a link to the site: check out the American Airlines jet there! awesome finish!!
www.alclad2.com