I've been inspired by some glass painting I've seen recently, particularly Tina Lugo, and other artists that paint the back of glass for a graphic look. I failed to find a pen I was satisfied with on the slick surface, so I created a makeshift one of my own. I filled a small bottle with Liquid Leaf, attached a syringe tip, and found if I squeezed with even pressure I could create a nice line.
I used this method to 'paint' my drawing outlines on the front of the glass, then I painted the back of the glass with simple acrylic colors. For the background I painted triangles onto a piece of plywood.
Overall I'm happy with the method, and will do a few more in the same fashion!