I just clean 'em up (inside stem and in & out on bit) with alcohol mainly to sterilize everything. Keep the cleaner off the external wood comonents. I save the salt treatment until I try smoking it first with some inexpensive and non-flavored mixture. You can try lightly scraping the coating inside the bowl with a pipe scraping tool (nothing sharp) and if the gunk you remove is soft and tar-like it needs a thorough cleaning. I would go ahead with the salt treatment.
A friend who quit pipes gave me his old ones and one had that soft-tarry coating. Don't know what he was smoking! It was like the tobacco never really got hot enough to burn well.
I bought two nice pipes once that had a huge build-up of cake. Like over half the bowl diameter. I removed most of it with my pipe reamer. They both ended up fine smokers.
