No expert but I did get a nice outcome with:
Bleach, whitening toothpaste, rubbing compound, a dremel, various dremel bits and lots of patience. I did an NOS GMT Pepsi insert and it took a couple hours to get it how I wanted it. I used the dremel and some compound on a medium soft cotton wheel to take the gen finish off and then used whitening toothpaste with the dremel alternating between short baths in bleach to get the fade I was looking for. Probably could have saved time by leaving it in bleach longer after I buffed some of the finish off, but I was not going for the full ghost effect.
I tried just soaking it in bleach first but after an hour, nothing had happened. I think that is unusual but it was my experience.
I agree on buying a couple cheap inserts to try it on before a gen.
Last gen ghost fat font I saw for sale was 1k+.
Before:
After: