Filling gap at ceiling for crown molding
I am installing a small (8' ceiling height) crown molding in a bedroom. The longest walls are about 18'.
Background: I have always used drywall compound (premixed) to fill all holes and gaps when doing interior painting. This includes nail pops, and cracks with a backing tape. I have also used the compound for various other filling jobs, like along he floor trim and door trim, including the 45 degree corners if there are any gaps.
Question is should I use a filler, such as drywall compound to fill the long gap at the ceiling and wall where the crown molding interfaces? This filler dries hard and can crack.
Or, should I use something like the exterior caulk I use outside, caulk that remains flexible and is less likely to crack on slight movement between the ceiling/wall and the crown molding.
I note too that I use drywall compound to fill nail holes in wood (e.g., crown molding) that is to be painted. Should I use wood filler?