I did basically the same thing with my WTM Panthers (
http://kiwidave.pbworks.com/BKC-German-Armour) I tried soaking them in water for a while, but it seemed to make no difference, so as Tostiq says, very carefully scrapped with a good knife.
Inking, weathering and a coat of matt varnish helps hide any blemishes. Also, I read somewhere (here maybe?) that turret numbers etc were painted over in the field, so having old ones partly visible wouldn't be too terrible
