I pre-cut lengths of wire with a Dangerous Disk. For the ordinary range of clip sizes, I just need one length (it's between 3 and 4 inches, but I couldn't tell you exactly what it is). It never occurred to me to do otherwise. I keep my clip bender and spare blanks in my flight kit, in case I need a custom clip.
If you're making it from one continuous piece of wire, wedge a scrap bit of 1/32 or 1/16 plywood between the wires and use a Dangerous Disk -- that should give you plenty of room if you drink just enough firewater to still the tremors, but not enough that you get sloppy. Scrap bits of brass or tinplate sheet work well, too.