How to clean shop vac of oily residue?
Start out by soaking the hoses in hot water and blue Dawn dish soap. It's the best for dissolving grease and I'm not affiliated with them in any way. Then you'll want to thread a heavy string or rope through the hose and wrap one end around a big rag and pull the other end so the rag gets pulled through the hose. You'll have to do this a few times to get rid of all the residue. If your rope is long enough, tie the rag in the middle of the rope and you can just pull it back and forth without re threading it through the hole each time. Replace the rag if it gets too oily.