You can't really machine GID stuff once it cures. I mean, you can, but it'll either break, chip off, etc. If that doesn't happen, you'll still destroy the integrity of the glow particles.
What I suggest is machining (or cutting/sawing) a channel or some sort of dimple on the delrin piece and fill it with GID+epoxy.
Did a test last night where I used GID+epoxy in a silicon mold and it gave me fairly good results.
So rather than cutting a channel, I'm going to machine the delrin part, use the delrin part to create a silicon mold, and use the mold + GID+epoxy to create the final part.