Use Extenders to Avoid Do-Overs
The longer that paint stays wet on walls or woodwork, the fewer lap marks and runs you'll have to deal with. Lap marks are those dark, ugly lines caused by painting over an area that's already dry. If you can keep the paint wet longer, you won't have to worry about them. And the way to prolong the 'open time' of paint is to add a paint extender or a conditioner (Floetrol is one brand; at home centers and paint stores).
Pour all the paint you need for the room into a 5-gallon bucket, then stir in the extender or conditioner (following the manufacturer's recommendations). Because extenders and conditioners help level out brush marks and paint runs, you won't have to go back and fix them later.
Cut in One Wall at a Time
Spend Less Time Taping
'Tape creates its own set of problems, like coming off before you start painting a wall and pulling paint off the wall when you remove it,' Bill says. 'But I learned the hard way that you still want to tape baseboards—paint will always splatter on baseboards if they're not taped.'