I've been working on my icon series and trying to find good gel pens that work on black acrylic or black gesso. I think I finally found two good options for these pens. The pens are Pentel Sunburst Metallic Med. Gel in Silver and Gold. These come in a two pack from Hobby Lobby and you can use the discount coupon for them as well. The regular retail is around $4.00, so these are quite affordable. Here's some of the results of the line work using the silver gel pen. The center element is done with a white pearl paint.