Many people can be shortsighted when it comes to counting the cost of a house painting project in terms of time. While getting it done quickly is a worthy goal, making sure to do it right the first time can help ensure you don't have to do it again anytime soon. There is more than one way to approach each facet of house painting with some of them more efficient than others.
Removing Old Paint
The goal when removing paint from a surface to be repainted is a smooth field for the new application, not necessarily removing every speck of paint. If the paint job is in fairly good condition, start with a stiff brush and scrub off any loose or peeling paint. Use a stiff nylon scraper for tougher sections. Avoid metal tools, when possible, to prevent gouging. For complete removal, a belt sander or oscillating tool with rigid scraper blade works well. Use a heat gun to soften old paint that refuses to come loose. Use chemical strippers as a last resort, since they are slow and can damage the wood.
Repairing the Siding
Once the loose paint is removed or completely stripped, you will have a clearer picture of what repairs will need to be made. Fill small chips, scratches and vertical seams with painter's caulk. Do not caulk underneath clapboards; they need to breathe. Look for damaged areas larger than 1 inch square and probe suspected rot with an awl. If it easily penetrates further than 1/8 inch deep, it will need repair. Cut boards out of the siding along the bottom edge of the board above and on a vertical line a few inches out on each end from the damage. Pry the upper board up and remove the top portion of the damaged board with a hammer and chisel. Cut a new piece of siding to fit and nail it in place. Fill holes and chips with auto body putty, which dries much harder than wood filler. Sand it smooth for priming.
Apply a good-quality primer to the entire surface. This can be done with a sprayer for the fastest job, or a brush for best coverage. If you are using an airless sprayer, be sure to cover all windows, doors and other features that do not need to be primed with tape and painter's paper. Use a latex-based primer with sprayers for easier cleanup without solvents. Prime all edges and faces of the boards, but do not attempt to seal the seam along the bottom of clapboard siding, which needs to be left open for ventilation to prevent mold and mildew inside the wall.
Select a quality exterior latex paint to save time and trouble with thinning and cleanup. It also goes on faster. As with priming, a sprayer is fastest; however, it applies the paint in a much thinner coat that does not adhere as well, and will require repainting sooner, costing time in the long run. A brush is the best method for a long-lasting application. Whichever tool you choose, start from the top of the wall and work down to save time working on runs and drips, which can be taken care of when you get to the lower area. Start at one end of the house and work around to that end, painting everything that needs it as you go, rather than reworking the same section twice. In some cases a brush may be required to paint around edges properly. A roller with an extension handle may be a good compromise, since it is faster than a brush but covers better than a sprayer.