Use your screwdriver to remove the bath faucet, handles and other fixtures from the tub. Press masking tape over any fixtures that can't be removed. Spread plastic tarps over the floor and walls.
Put on your respirator, mask and gloves.
Brush etching solution over the porcelain surface of the tub, using your paintbrush. Cover the whole surface in a thick layer of it.
Let the solution etch the surface for 15 minutes. Rinse well.
Load your paint sprayer with primer. Spray it on in a thin, light layer. Keep the sprayer moving at all times to avoid drips or ridges.
Allow the primer set for four hours. Apply a second coat in the same manner. Let it set for 12 hours.
Fill the paint sprayer with clear-coat paint-polyurethane compound. Spray it in the same manner as before, in a thin, light coat. Let it dry for four hours.
Spray on a second coat of compound, let it dry, and repeat. Continue until you have sprayed on at least four coats, to the desired finish. Let the final coat set for two full days before reinstalling the fixtures.