The house bath may reveal nails that have popped out of the siding or rusting nail heads that have left streaks of rust on exterior walls. If so, use sandpaper or steel wool to clean the nail heads. On clapboard siding, use a nail set to recess the nail head about ⅛ inch below the surface of the wood. Dab on a coat of rust-inhibiting primer (unless the nail is aluminum or nonrusting galvanized steel), and let it dry. Then fill the nail hole with spackle or putty. When the filler is dry, give it a coat of primer. For flathead nails, which cannot be recessed, sand the heads until they're shiny, and coat with primer.
Keep an eye on the new cans as they're being brought in. Make sure they look new and don't have paint in the rim of the can. If it's a five-gallon bucket, check to see whether the lid is still sealed on with the plastic strip. The only time it's acceptable to mix water in the paint is when you're using a deep or ultra deep base paint to reduce its stickiness, which is rare with new paint technology. Dark primary colors are composed almost entirely of tint that makes it very hard to work with without adding water.
I did go with the highest bidder and it did not matter. They did a shoddy job and threatened to take me to court when I pointed out mistakes that they made based on their work standards stated on the quote. I have not paid them yet, just filed a complaint with the BBB. No money down asked, no contract signed. The boss stated I have to high of expectations just because I live in a 121 year old house!
They painted our home exterior about 12 years ago and did the interior about 9 years ago as part of a major remodel. As it was time to re-paint the exterior again, we used James Lee again, and were very glad we did. In walking around to find 'punch list' corrections after they were done, there was pretty much nothing to find - they did a great job.