For your shower arm, I would use teflon tape then pipe dope. Never fails me. On the drain you can just use pipe dope if you really want to.
I use any brand. Normally ones I pinch off licensed plumbers when they pay a visit for difficult work. You can get so much off plumbers. I've nabbed sandpaper, copper fittings, pipe, dope, tape, flues. They never say no. Could be the $500 call out fee I give them.
Next I might try to nick their torch. After that, their van!