1. Wash. You’ll be painting only the exterior of the tub. Check that any existing exterior paint is intact and not flaking off. (If it is flaking, you’ll need to have the tub stripped or sandblasted first so the new paint won’t peel.) Position the drop cloths. Wearing gloves, wash the exterior of the tub with water and the cleaner or deglosser. Clean as much of the outside of the tub as you have access to. Let dry.
2. Apply the tape. Apply the painter’s masking tape to the top edge of the tub feet or to the floor around the feet, depending on whether you are leaving the feet with their existing finish or are painting them. Also apply tape along the top rim of the tub, to keep the interior paint-free.
3. Treat the rust. Inspect the tub exterior, and the feet if you plan to paint them. If you find rust, use the brush to apply the rust-bonding primer over those areas (this chemically converts the rust so the paint will bond to the surface).
4. Prep and prime the surface. Don’t sand, as you normally might before priming, because the existing paint is likely to contain lead. Pour the shellac-based primer into the paint tray, and use the roller to paint the main areas of the tub exterior. Then use the brush to smooth out the finish and fill in where the roller won’t reach, such as the under-side of the tub rim. Prime the feet, too, if you plan to paint them.
5. Paint the exterior and feet. Apply the latex enamel in the same way you applied the primer. (Skip the feet if you’ll paint them a contrasting color—see Style note, below.) When the first coat dries, apply a second coat if needed. Let dry.
If you need to paint a tub that is close to a wall, wear long rubber gloves when reaching between the wall and tub (to protect your arm from paint) and consider using a sponge to apply the paint.
Don’t worry if you leave gaps along a tub edge that you can’t see. The paint is just for show, so gaps you can’t see don’t matter.
For a classy look, paint the feet a contrasting color. White feet look especially sharp on a tub with a white interior. Metallic paints are another option.