I recently painted some Masonite material that had old oil based paint on it. I sanded it and applied latex enamel, with eggshell finish. I did not use a primer. After drying several days, the paint feels tacky and when objects are place on the surface they stick enough to pull the paint off. What do I do now?
Some water based paints can take a long time to harden, this is true for semi-gloss. You could leave everything off and just wait for a few more days. If the paint is still tacky you will need to prime it and start over. Use a good quick drying oil base primer, regular Kilz or Zinsser Cover Stain should work.
The primer won't fix the paint underneath but it will form a hard film that can be painted over.
Check out <a href="http://questions.house-painting-info.com/how-do-i-stop-my-books-from-sticking-to-shelves-that-have-been-painted-with-a-latex-paint.html">How do I stop my books from sticking to shelves that have been painted with a latex paint?</a> for more information.