I am restoring a bathroom in a historic fieldstone home. The interior bathroom walls are fieldstone. Most of which have already been painted with off-white latex. Some stones are unpainted. Water from the shower head will the be hitting the fieldstone walls in the corner shower. I have prepared the surface and filled in all the cracks with latex caulk.

What is the best primer to use? Oil-based or latex?
What is the best topcoat to use? Oil-based or latex?

I prefer Benjamin Moore products.

I'd have to say oil base. Make sure all coats are fully cured by manufacture recommendations. Also ask the person at the Benny Moore paint store what they recommend.

i am restoring a bathroom in a historic fieldstone home. the interior bathroom walls are fieldstone. most of which have already been painted with off-white latex. some stones are unpainted. water from the shower head will the be hitting the fieldstone walls in the corner shower. i have prepared the surface and filled in all the cracks with latex caulk.

what is the best primer to use? oil-based or latex?
what is the best topcoat to use? oil-based or latex?

i prefer Benjamin Moore products.
You could use pool paint/marine paint if it will be in direct contact with water every time you shower. If not use oil base.. naturally repels water (both pimer and finsh) any paint store/hardware store can point you in the right direction.