As a member of the Texas GSP Rescue, I have rescued a bunch of GSP's and several of them have turned out to be great hunting companions. The first obstacle is you (not you specifically), but the owners own mindset. It's a GSP...forget that it's a rescue. Train him/her up as you would any other GSP. No, he/she won't have the high dollar pedigree but a hunter is a hunter. Pictured are GSP's Gus and Taz and Lab Seal...both GSP's are rescues and probably have over a thousand birds under their collars. Taz was rescued at 3 yrs old and is now 14...Gus is 7. The old guys in the picture...well...they're old guys!
If they didn't want me to have a midnight snack, then why did they put a light in the refrigerator?