the goop traveling up the stem
Zanthal, Bigvan, Jud, etc.. have given you some good advice already.
Personal experiences
1) I dry my tobacco. Almost always except with the C&D blends. They seem to have just the right moisture right out of the tin. SG on the other hand is probably the most moist (is that a word) right out of the tin and can use several hours of drying.
2) Smoke slow, sip, don't suck ;-)
3) Even with all that, I still get a gurgle on occasion with certain pipes. It's just part of the joy of pipe smoking. The famous wrist flick or a quick pipe cleaner usually take care of that. But even with a gurgle, I seldom suck that hard on the pipe that I get much "goop" in my mouth. The
occasional dribble of moisture or a fleck of tobacco is inevitable, but not goop :? If you're really getting goop, gunk, whatever.. I'm suspecting you're really drawing too hard.
Good luck and don't give up. It gets better with practice and time.