I've painted hundreds of bevels for non-conservation work. I usually use fine tip Pentel markers that I get from United. Does anyone know of any type marker or paint that would be safe to use in archival framing?
You can use acrylic paints like Folk Art, or Ceramcoat. Any acrylic paint is acid free. Just remember to not have too much paint on the brush. I usually use 3M magic tape, it is available 2" wide. Mask off the front of the mat, then cut your opening, make sure your tape is covering the edge securly. Paint the bevel, then carfully remove the tape.