A qualified exterior house painter can walk you through the process of getting your house ready for a new coat of paint, from scraping and sanding to patching and priming. A pro can also recommend the best exterior paint for the job, whether your siding is wood, fiber cement, stucco, vinyl, or even metal. When it comes to getting the work done, your painter will arrive with all the tools and equipment needed to get the job done quickly, correctly and safely.
If there is any peeling — and there usually is somewhere — it's essential to scrape off any loose paint. This doesn't just mean the parts that are already separated from the wood and ready to fall off on their own. Each spot where paint has peeled loose needs to be scraped thoroughly until you can no longer get the sharp corner of a putty knife under any of the surrounding edges of paint. Then, the bare spot needs to be sanded until the paint edges are smooth.
My wife and I just painted the interior of our house with about 6-8 gallons, of $30+ per gallon (meaning the good stuff, non-diluted) with absolutely fantastic results. However we just paid an average of $5 per gallon. Reason...all big box stores have paint, set aside, that has been mixed but not picked up by the customer. They need to sell it quick and if you're not in a hurry (you know well in advance that a room or two need painting and it's not like the roof leaking and needs an immediate fix) you can go to each store when you need other supplies or food, like Walmart (when convenient, driving 20 miles to each is not worth it) and over the course of a month or two, pick out some very nice colors of quality paint. We found perfect colors...not saying they were our first choice but when we opened the can, very nice and some even better than our original picks. Cost to paint the entire house was about $100, with all materials included, period. We had it on the market for a few months to sell, didn't sell, painted the rooms, got 2 offers the day after we finished, took the best one and never looked back.
Sorry it is difficult to trust almost anyone in the trades. It is easier to do the work myself and not deal with strangers in and around my house. When I have to hire someone I tell them up front that I'll be checking every detail, pay extra to purchase the materials myself, and if they don't want the job - well good! I always fine someone who will work with me as I pay a bonus for that.
If less than half the old paint is left, however, it may be worth stripping it all off. Guertin gets rid of stubborn remnants using shrouded grinders (like the PaintShaver), infrared paint strippers (such as the Speedheater), or chemical strippers (like Multi-Strip), then smooths the wood with a course or two of sanding. When siding (or bank accounts) can't take the shock of a total strip job, Rich O'Neil, of Masterwork Painting in Bedford, Massachusetts, has successfully hidden rough, well-adhered paint under Peel Bond, a thick primer.