I used the oil-based original Kilz to block some water damage to my
popcorn textured ceiling. Then I repainted with a flat finish ceiling
paint but the area where I used the Kilz is very glossy whilst the
rest is flat (as it was supposed to be). Anyone got any ideas about
how to proceed to flatten the gloss? I'll redo the ceiling if I have
to but I don't want a glossy ceiling.

Agkistrodon