If paint is poorly applied to something with little care taken when doing it, the paint will look blotchy, leaving some spots saturated in lots of color while other spots will barely have any. If this happens, you need to repaint it. Before repainting it, you need to apply primer. This will help keep the new coat of paint even and prevent blotching.
Things You'll Need
Bucket of soapy water
Wipe the blotchy paint job down with a sponge soaked soapy water to remove any buildup. Dry the painted area with a towel.
Paint a coat of primer onto the paint job. Make even strokes so that the primer is evenly applied. Allow the area to dry for about two hours.
Paint the area with the original paint. Just as in Step 2, use even strokes to paint the area without any stroked being visible.