Thread sealant is mainly a lubricant for the threads. I've even used a bar of soap in a pinch on tapered threads.
You can use pipe dope, or tape, or both.
I'll be replacing my Tee this week. I had used pipe joint compound(Ace hardware brand in tube) which is leaking? I've since picked up a can of Rector-seal 5 (slow-dry/soft set) and a roll of "blue monster" teflon tape for final repair. tank and elbow are new as well. Other than the tube compound being what appeared to me as just too wet/loose(even after kneading), I figured I better turn to the experienced to improve my luck!
I have found that rector seal #5 works excellent. Make sure to mix it really well and let it "air" out a little before using.
you guys think 2-3 wraps with the blue teflon tape then some rector seal will be good??