So second mold is finished. I tried a rough run with decorating gel made by Eberhard Faber. Some things worked; some didn't. Here's what I found...

The Farnell buttons embedded in the mold before casting worked well. Use the shortest (16mm). The 19mm give too much of a halo within the buttons.

The decorating gel tears too easy (the 4th button tore apart) but is flexible when it sets up. (Flexible buttons are very cool.) The color is about right for white glow buttons. It's tough to tell in the photos but they have a frosted glass look to them.

I tried another batch with black pigment to attempt the color discussed above but the buttons came out with a purple color and glow with a wine tint.

The mold itself needs work. I'm using a silicon RTV rubber that can take high temperatures. The button tops cast clean but the sides are a ragged. I didn't take into account the farnell buttons blocking the sprue holes.

I also tried some FIMO clay for the knobs but they crumbled when I tried to pull them from the mold. The Sculpey clay seemed to work better.