preping plaster walls for painting
I do a ton of old houses like that. If the plaster needs repair ( and they usually do- as in cracks) I "suture " either side of the crack with sheetrock screws into the lathe- is tricky to do right- and then use screen tape- and 1 coat mud to set ( usually a powdered "hot mud" , 2 more to fan out.
Same with any imperfections- you can use premixed Plus 3 - use a wide blade whenever possible.
sand smooth, prime with a primer sealer ( I've been liking smart prime lately- low voc- thin so it penetrated, great adhesion).
Then look over touch up as needed and finish.
you can use caulk in corners- i would do that after priming.
"It's better to come here with questions before you screw up than to come here after and ask how to fix them."- JS