you have to be careful to clean the wall of any grease -- primer is very sticky and somewhat diminishes that need.
re unusual paint: the house i owned in seattle had a 16 x 20 living room with a dark brown ceiling. primer was a necessity.
you mean, i should not have have spread lard on the new plaster walls?
it's fine as long as you clean them off. but you should have painted them before applying lard.