I spent the last 4 weeks removing paint and sanding the stair railings and the big corner posts [newels?]. Don't ever do this if you have arthritis in your hands! They are about 100 years old, had multiple layers of paint over varnish and dark stain. After sanding the railings came out pretty good but the big posts still had the dark stain on them and generally didn't look very good. I stained them anyway with Minwax Jacobean and the big posts are horrible, black in some places, no grain showing---just ruined. I would never put varnish on them. The railings are good. So now I am going to paint the big posts a dark brown. What primer should I use directly on the dark oil based stain? Should it be tinted? I want to topcoat with a satin latex. Thanks.