Last time we chose a roller; now it’s time to paint. Pour enough paint in your tray to cover the bottom reservoir only. Roll your roller in the paint to cover the entire nap. Then even it out by lightly rolling it on the shallow area of the tray. Don’t squeeze out the paint; the key to a good roller job is keeping plenty of paint on the roller.
You might think it’s best to paint in straight lines, but a random pattern of strokes covers all the tiny irregularities in the surface, and minimizes the chances of lap marks, where dry paint is covered by fresh paint. Start by rolling upward to minimize dripping, and roll slowly to avoid spattering. With flat paint, apply your random pattern, get more paint, and continue. With glossy paint, finish the job with vertical strokes to get a more even look.
Your roller may fail to roll at times. This can be caused by the roller sliding on the sleeve or by the actual roller cage sticking because it’s clogged with dry paint. This leaves a track which will show up later. Keep your roller clean, and don’t press too hard.
If you’re going to use the roller later that day, store it in a tightly sealed plastic bag (you can freeze it, but thaw it out completely before reusing). If it will be longer before your next paint job, clean up. Roll it on newspaper until paint no longer comes off; this might take a lot of paper. Wash out latex paints in a sink, squeezing by hand. Wash alkyd paints in solvent, wearing rubber gloves as you squeeze. Give it a good spin when you’re done and let it dry. Then store it in a plastic bag.