If you really like the gun and are willing to put someserious work into it;
Clean off the original finish
scrape to a polish with the edge of glass [becarefull !!] tape and pad your hand grip.
Buy some Tung nut oil
Rub on lightly wait a day and rub out
I do this for 16 coats and repeat through the life of the gun as needed .
This is the finish my Grandfather use on the guns he made ,I think it goes back a ways but I really don't know I do know that it gives very good results if done right.Lee