Cutting In

• "Cutting in" is the term for painting all the corners and edges with a brush before rolling. When painting walls, cut in first, then roll the paint on. This eliminates brush and roller marks. Brush a stripe down each inside corner extending the paint about two inches onto each wall. This makes it easy to roll without bumping or scraping your roller into the corners. When cutting in along the ceiling, brush down about four inches. This makes it easier to avoid hitting the ceiling with your roller.
  
  

Painter's Tape is Your Friend

• You may be painting an accent wall or have a color change from one wall to the next. Unless you have a lot of experience and a very steady hand, painting clean, straight lines in corners and along trim requires taping with blue painter's tape. Unlike regular masking tape, blue tape seals the edge tightly and is easier to peel off cleanly when you are done.
  
  Lay the tape in the longest length you can, instead of using short pieces. Press the edge down firmly. If the surface is smooth, this is all you need to do. Wait two to four hours before removing the tape.
  
  If the surface is textured or rough, ensure a straight line by painting a thin stripe of the opposite wall color (the surface you have laid the tape on) first. Allow this to dry for about an hour, then paint your line with the accent wall color. This "seals" the edge and prevents bleed-through of the second color. Another trick to help even out rough edges is to run a generous bead of caulking down the corner, smooth it out and let it dry before painting. This provides a smoother line along the corner. These techniques work for the corner along the ceiling too.
  
  

Professional Tips and Tools

• Use high-quality tools for more efficient painting and better results. For faster painting of interior corners or exterior corners, consider a corner roller. These are small doughnut-shaped foam or fiber rollers that make quick work of corners.
  When painting two coats, consider thinning down the first coat of paint with no more than one pint of water (or solvent, for solvent-based paint) per gallon. This makes the paint flow easier for making straight lines in corners, and also covers rough surfaces more efficiently.
  Adding a paint conditioner to the paint also improves the flow consistency and coverage. This is particularly useful for painting straight lines.