When painting interior trim it's all about the prep work. First make sure to wipe down and vacum all the wood. second, give all the trim a light sanding and fix any imperfections with wood fill. Third, caulk all the gaps you can see. After the caulk drys, there is a great product from white lighting called bolt quick dry this drys in 30 minutes and is easy to work with. then sand any repair work down to trim. Finally prime any repair or bear wood spots with zinnser cover stain. okay ready to paint.