Removing the gloss from your enamel painted surfaces is a simple process. You have the option of using the more traditional sandpaper option to remove the shine or you can use liquid sandpaper. Both options have their pros and cons. So just use whichever method you feel comfortable with. Use caution and good sense as you work, though, or you may ruin the paint surface and have to repaint.
Using Traditional Sandpaper
Lay a tarp down below the painted area. Bring the edge of the tarp as close to the wall as possible to prevent paint grains from reaching the floor.
Wash the painted surface with hot water and soap. Remove any dirt or debris from the wall that will interfere with the sanding process. Let the wall dry before you attempt to sand it.
Sand the wall surface with 400-grit sandpaper. Don't use anything coarser than 400-grit sandpaper or the scratches will be visible. The fine grains on the sandpaper will make small, unnoticeable scratches that reduce the glossy-look of the paint surface.
Dab the painted area with tack cloth -- a sticky cloth that leaves no residue on the wall -- to remove the paint dust. Repeat the sanding process if the painted area is still too glossy for your liking.
Using Liquid Sandpaper
Don a pair of gloves and goggles to protect yourself from the harsh cleaning chemicals in the liquid sandpaper. Tie your hair back as well and don't touch any other part of your skin until you remove your work gloves.
Wash the paint surface with warm water and soap. Dry the surface with an absorbent cloth.
Open the lid on the liquid sandpaper bottle and place a thick cloth over the top. Flip the bottle over to apply some of the contents to the cloth.
Scrub the painted surface with the damp cloth. Move the cloth in a circular motion as you work. Rinse the cloth as you work to avoid a buildup of debris.
Allow the liquid sandpaper to dry, per the manufacturer's recommendations. Wipe down the painted surface once again, of it is still too glossy.