I've used a dremel with the small wire wheel.

What about goof off? Wouldn't a wire wheel scratch the receiver?

Try a rag with acetone (mask off the reciever), just wipe some on and let it sit for a few seconds then repeat.  I think my buddy actually stole his girlfriends fingernail polish remover to clean his in a pinch.

Acetone is something you don't want to be spilling everywhere,take care when using…use isopropyl alcohol for a final clean.  Depending on the amount of glue it may take awhile, they all vary.

Just use some quality gun solvent on the glue, just let it soak and do some scrubbing, That is all I use.