Gino, if I used an oil based, would I still have to get all the old paint off? Of course I will sand off the best I can, but in the nooks and crannies of the carvings I won’t be able to get everything off. I will do the best I can.A good water-based primer will be just fine. However, you need to get ALL of the paint off down to bare wood, in order to prime the old wood again. You shouldn't prime over old paint whatsoever.