I have a couple of engraved rifles, A Tolley from 1894 and a Hollis from a similar era. The engraving on both has filled with a mixture of sweat, dirt, oil and other substances only wondered at to the point where it has achieved the strength of epoxy

this has left them looking muddy and ill-defined. I don't want to go the way that some have of heavy duty buffing until it shines like a mirror nor even removing the smooth grey patina (I figure it's worked just as hard as I have to get that grey)

Any suggestions to just remove the concreted guk from the engravings but leave the overall patina in place? Free beer to the best answer when you visit the Eagle Park Range near Geelong in Victoria!
Cheers
Oz