Preparation is 90% of any good paint job. There is no exception to this. We take pride in doing thorough prep on every job we do, we want your investment to last for many years after we leave. A month long exterior painting project can be over three weeks of cleaning, scraping, sanding, priming and caulking. The painting normally only takes a short time, comparably.
Another important part of preparation is purchasing high quality materials such as caulk and primer. It's always a good idea to spend a little more on these items because if these fail the whole job fails. Of course its important to use the best possible paint too, but if the preparation isn't done properly, it really doesn't matter.