ps I've had an idea for a better spark sustain, but leave it till you've got the basics going.
FWIW, the "disintegraters" I've used (for removing broken taps, drills, etc.) used an axially vibrating electrode holder that slowly lowered the electrode to the work piece, (the electrode never actually touched the work piece), the fluid (DI water) was pumped through the hollow electrode and kept the electrode cool as well as flushing the particles out of the hole.
Progress again.... DI water is MUCH higher resistivity than RO - . And both have far lower viscosity than veg oil, and would clean your work much better. As would kerosene.I'll knock up a crude drawing of my squashed hole idea.What about piano wire ? stiff and strong... and obtainable in very fine gauges.Allan