I have a number of walls that have a mix of old lath+plaster and new drywall (parts of walls are plaster, other parts new drywall). The old plaster walls have paint on them but they have not been painted in a long time (like 6 years).
I am aware that there is Glidden Duo primer+paint mix which saves time (2 vs total of 4 coats with priming and painting separately). However, given the nature of the walls and the integration of the old and new technologies, as well as the fact that the old parts already do have paint but the old ones do not, I am not sure if I can go with Duo or if I should prime it first and then paint it.