~sand surfaces lightly...I use a small electric palm sander, which makes the job much easier.
~wipe it all down with Klean Strip Easy Liquid Sander (this product can be used instead of sanding, but I do both to guarantee the paint will stick!)
~prime surfaces with Zinsser Bull's Eye 1.2.3 Interior/Exterior Water Base Primer
~paint with 2 coats of a satin or semi-gloss latex paint
Then I painted a piece of beaded board plywood that was cut to fit and attached it to the back...On the window, is the Scandinavian blind -- yes, it's finally finished -- a project from Katrin Cargill's book Simple Soft Furnishings.