Lettering Help....

[Steamtrains]

I'm currently on a lettering/numbering binge...(got to do it while I'm hot...), but need to remove some lettering on one of the locos. I try to purchase all my locos painted/unlettered, but this one was a gift, so it came with lettering. So what is the proper way to do this without ruining the finish on the loco..??

Any suggestions would be much appreciated.....