I dipped my case for cleaning... didn't work out the way I needed it to.
Hot Soak Thread
Then I basically used 00 steel wool on the outside and non-machined surfaces. Lots of elbow grease.
I did see a case that looked like it was brand new. Ollies has a media tumbling method (NOT blasting) that makes it look like it just came off the final machining center at Porsche. Its amazing. Only $100 + $130 to clean out all the media and replace all the gally plugs etc... They also do good machine work so you may find your all-in-one solution there...
-Michael
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Michael 
'82 Euro SC 'Track Rat' 22/29 Hollows, 22/22 Tarrets, Full ERPB F/R, Rennline Tri Brace, Glass bumpers, Pro 2000's, 5 pts, blah blah blah
'13 Cayenne GTS