On mine I apply the epoxy, then put them on the spinner. Use a pair of vise grips to hold the wire while applying epoxy. I have a few different sizes of springs that I'll use depending on the size of the plug. Spring goes on one end, a piece of wire bent into an S-shape on the other. Definitely have to make sure the plugs are held tight or the epoxy will sag. If I do less than 12 plugs, I space them out on the spinner so that the weight is distributed evenly.
BM
Jigman