A mad scientist answer to this problem:
The best option is to make the PoCo do it... its a dangerous operation that requires a specialized tool.
You would need a high voltage resistor (for safety, it MUST be rated for more than the expected voltage!) connected with high voltage cable to high voltage probes.
It could be built but beware, cut corners on the apparatus and DIE.
Building this is an exercise in engineering. You cant use just any HV resistor...it will be dissipating significant power and you don't want to burn it up. HV resistors cost $$$ and if it fries, it might arc over!
The whole thing would need to be potted in pure silicone for insulation.
Approximate calculations assuming a 200 watt resistor being fed 13.8kV... a 2Mohm resistor would do. (it would be well under its 200W rating at 13.8kV which is necessary considering its going to be potted)
What's scary is even if you build this thing and insulate it well AND you verify that the bank is at 0 volts....as soon as you take off this device, it may begin to partially recharge. The phenomenon is called dielectric absorption....charges in the dielectric migrate toward the plates and put some charge back on them! With a big cap, this residual charge could make you a crispy critter.
To prevent this, the caps must be shunted after discharging them.
Take all that in before tackling this. Safety issues aside; the tool could easily cost a few hundred dollars to make a safe one. HV probes, resistors and cables are expensive.
