Unless you like textured walls, don't paint over dust. Wash the walls with trisodium phosphate (TSP) or a mild cleaner, like Jasco's TSP No-Rinse Substitute. For smoke-stained walls, Toto uses a 50/50 solution of bleach and water. To clean a wall, use two buckets. Load up your rag or sponge from your cleaning-solution bucket, and scrub. Before redipping, rinse the sponge in a second bucket filled with clean water.
I put out a request for bids to several local house painters and quite a few seemed high. One was for over $6000 for painting the exterior of the house with putty fill as necessary, paint included. It was for him and one other guy to do the work. I said, "it's going to take you guys quite a while to get this job done" and he told me that no, they could do it in 2 days. I don't know about you but $1500 a day per painter seems more than just a bit high. I went with someone else and they had several people there for several days working like crazy and did a great job. There are too many scammers.