Step 2: Prep the baseboards with painter’s tape. If there’s any existing caulk, remove as much of it as possible; a putty knife, 5-in-1 tool, or wire brush can help dislodge the old stuff.

Finish by applying tape to the tub or shower floor. Cut the nozzle tip to match the gap width. Hold the gun at a 90-degree angle to the gap and push a bead of caulk slightly ahead of the nozzle as ...