A friend recently gave me an old grainfather that was in a flood and left to sit for a few years so it had a bit worse than dried wort on it. I used a damp rag and wiped off the majority of the loose debris and sprinkled some barkeeper's friend on it and scrubbed it clean followed by another wipe with a clean damp rag. After rebuilding the pump and putting new bearings in it and boiling all of the silicone bits I filled it with water and PBW and heated it to 140*F and recirculated with both the sparge arm and the counterflow chiller for about an hour or so. The controller did have some old wort on it but a damp rag took care of that. I've already brewed 4 batches on it with no issues(just the typical problems learning new equipment).
I guess what I'm trying to say is if there's any stains that just soapy water won't get off then barkeeper's friend will make it look like new, these units are pretty resilient.
