Work From a Paint Pail
Rather than dipping your brush into the gallon can the paint comes in, transfer a small amount to a paint pail. Pour only about an inch of paint into the pail. A small amount of paint prevents dipping your brush too deep, reduces weight and expedites cleanup if you spill the paint. You can buy special plastic paint pails with handles built in or a metal one like the one shown here. An empty paint can with the rim removed also makes a great paint pail. You can remove the rim with a kitchen can opener.
Pat, Don't Wipe, to Load the Brush
Dipping the paintbrush and then wiping off the paint on the edge of a bucket is a common practice, but it's not very efficient. It's better to leave more paint on the brush by dipping the bristles about an inch into the paint and then just patting the brush against opposite sides of the pail. With that amount of paint on the brush, you'll be able to cover more surface before you need to reload.
Wiggle Into Corners
Wiggling the brush a little bit helps the paint release into tight corners. Wiggling the brush is also a good technique for filling in missed areas as you make a second pass. Don't wiggle too hard. Just a little vibration is all that's needed to get great results.
Mask Only the Tops
When you master cutting in, you need to apply masking tape to only the tops of windows, doors and the baseboard. And the only reason you do this is to avoid spattering the woodwork when you roll paint onto the walls. Masking less saves you time and money, and you don't have to worry about paint creeping under the tape or the paint job getting messed up when you pull off the tape.
Buy a Good-Quality, Angled Sash Brush
We've seen many pro painters cut in perfectly with a big square-edge brush, but for most people, angled sash brushes, like the ones shown here, are easier to control. You can fan the angled tips out to get a fine line of paint, and the angle makes it easier to get into corners. A 2-1/2-in.-wide brush is about right for most interior room painting. But if you're painting windows or other small woodwork, buy a smaller brush too. It's easier to paint accurately with a smaller brush.
Get in a Good Position with Bright Light
To paint an accurate cut-in line, you have to get your body into a position where you can see the line clearly, and you need bright light. One of our Field Editors sent us this tip—to use a headlamp—and it really helps. For cutting in along the ceiling, get your head close to the ceiling for the best view of the cut-in line.
Work Up to the Line
When cutting in against a ceiling, molding or other surface where a straight line is required, start by sweeping into the line to unload some paint onto the wall. Don't worry about getting close on the first pass. Without reloading your brush, make a second pass to coax the paint closer to the line. Fan the bristles so you're using the tip of the taper to spread the paint in a straight line. You may even have to make a third pass to get a perfectly straight cut-in line.
Mix in Conditioner for Easier Brushing
Paint pros we talked to recommended adding conditioner to the water-based paint you'll use to cut in. Ask at the paint store for paint conditioner or paint extender. Either one will work. Our paint consultant just dumps a little bit into the paint pail each time he refills and then mixes it up. But if you want to measure, we recommend about one tablespoon per cup of paint. The conditioner helps the paint flow easier, which in turn makes it easier to apply the paint in a nice crisp line.
Wipe Off Goofs
Even pros occasionally get paint where they don't want it. One method of cleaning up goofs is to wrap a damp rag around a putty knife. Make sure the cloth is only one layer thick for the most accurate cleanup. Then carefully slide the putty knife along your goof to wipe it off. You have to do this right away, though. Once the paint starts to dry, you'll have to use more aggressive measures.
Feather the Edge
When you're happy with the cut-in line, finish up by feathering or thinning the edge. Without reloading the brush, drag the tips of the bristles lightly over the outside edge to spread the paint in a thin layer and get rid of any ridges or paint buildup. This feathering step ensures that your cut-in paint won't show as a stripe after you roll paint onto the walls.