Begin by using a brush that has lightly water-dampened bristles.
Dip the brush into the paint to about one-third of the total length of the bristles.
Remove the brush and dab it on the tray or the inside of the can a few times to remove excess paint. Don't wipe the brush against the rim of the can as the rim will fill with paint, making the opening and closing of the lid messy and difficult.
Repeat this at least twice to make certain the bristles have taken up the proper amount of paint. If the brush is properly loaded, you should be able to move the brush without too many drips.
Remove any lint by lightly pressing painter's tape on the roller cover.
Lightly dampen the roller and remove any excess moisture with a paper towel.
Roll the roller cover into the deep end of the paint tray. Do this several times to cover the entire surface of the roller cover with paint.
Roll off excess paint onto the shallow end of the paint tray.
Repeat these steps several times to ensure the roller cover is entirely saturated with paint. A properly loaded roller should not drip when moved and does not require you to apply force against the surface to transfer the paint to the wall.