Sand to key, then apply an acrylic primer/undercoat followed by two coats of acrylic eggshell or satin. Best trade acrylics are Leyland & crown from experience
Acrylic primers don't stick very well to varnishes. Best bet is to take the door off and paint with oil based undercoat and bring it in when they have dried.
True Joe,you cant beat oil-based in any situation, thats all Id use, though Jessie had said stained doors which she could get away with in acrylic primer.. Jessie ,if you can put up with the whiff or take the door off then go for oil for all coats - much easier to use & less brushmarks
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