We're painting the interior ourselves. This means we're also prepping the interior ourselves. Originally this wouldn't have been too bad, since the house came prepped and primed from the factory. But then we ripped out about 400 square feet of various walls and ceilings for building inspections and rework.
The plasterers who finished the attic also did the patching. They tried to use plaster as much as possible, but where they were joining with the factory drywall they had to use joint compound (mud).
I didn't fully appreciate the difference then, but I sure do now. Plaster veneer is skimmed on, flat and level, and is extremely hard and virtually unsandable. It has to be done right the first time. Drywall mud is soft and sloppy, and cannot be done right the first time. Instead, you put too much on and then sand it off flat. This took me a week of late nights, generating more than 10 pounds of fine dust.
But now all the plaster/drywall is prepped pretty well, with a coat of a sealer called GARDZ that seals in the alkaline lime plaster for painting.