Silver markers tend to leave streaks because each line does not "blend" with one another. I would look for a silver paint pen that leaves a decent layer of paint that could be blended into itself for a nice smooth, even-colored finish. I've tried coloring things in with silver sharpies and the individual lines show. A paint marker/pen may drip if used on the side of the rubber bands so maybe a sharpie for the sides where the surface area can be covered in one marker swipe. That way you don't drip silver paint marker on all of your hard work
