First scrape putty and apply primer together. Then paint a lighter color first, and go past a little dividing line. Paint the lighter color 2 to 3 times. Wait for it to dry, and then use textured paper (preferably the kind with plastic sheeting) to cover it. After the dividing line is posted, another color should be applied as soon as possible. When the paint is 60 or 70% dry, the masking paper must be removed. If it is removed too early or too late, it will easily cause the dividing line to be uneven.