Hmm I've never tried that. I've heard of the gold coating rubbing off due to general use, so I'm trying to take better care with mine!
Sounds like it would work, but it sounds like it has the potential to get messy. Would it be possible to take it to a professional to do a touch up before you try anything? It'll probably be worth it if they can get it looking new again. Not sure if Prada offers that kind of service though.
I'm actually wondering a out the same thing on my month old wallet. I unfortunately was in a hurry when I bought it. I looked at and inspected the wallet in the glass case. The. The SA got an untouched one from the back. I should know better, but I did not inspect the logo, just the hardware and leather. Luckily, I bought it at a Saks. I'm taking it to the local Saks next week. Surely, they have a cloth or cream or something?
I just checked it again. It seems it is tarnishing everywhere.