The process is an electrically applied deal. They dip your body into a solution that's copper-based that adheres to the existing finish. That's why they won't do a bare-wood one...has to have finish to adhere and also so it doesn't soak into the wood.
It then has an electrode attached and goes into a pool of the metal of your choice with the opposite charge, and that's the deal.
I had this idea too, and was warned by Rich when i asked him about it before I did it. So rather than send my nice guitar to them and have a hack do a crappy job and ruin a nice guitar, i sent a dummy body. A junk
strat body i had laying around. It came back basically unusable. The area where the neck pocket has been "cleaned up" by them had grinder marks where they tried to get the excess playing out, but took wood too...I complained, and they said try again. I had another body available that was just collecting dust. The guy said he'd try using a different machine to clean it up. That body came back even worse. I actually threw both of them away...
So, I bailed on the idea, and bailed on LGM, who was into making an inlay for me. It sucked and I'm still dreaming of that guitar...just need to do it another way. Don't send your guitar to these guys unless you want a guitar-shaped paperweight. If it's still playable, it's only after you finish cleaning up their mess, and by then, you are just too pissed off to deal with it and want your old guitar back...