Caulking: Remove old caulk. Spray with bleach diluted to 10% to remove any mold. Fill tub with water. Place tape 1/4" from crease. Squeeze deep into crease. Smooth out with wet finger. Then peel off the tape immediately, before it dries. Drain the tub when caulk is dry. Wait 24 hours before using tub.
How to Caulk a Perfectly Straight Line — 1) Squirt caulk into taped off area. 2) Smooth caulk with fingertip. 3) Continue smoothing. 4) While caulk is STILL WET, slowly & gently pull up the tape.