I used to repair cardiac defibrilators and we discharged the giant capacitor used in them with a high voltage probe, The high voltage probe was originally used to measure the CRT votage on the side of a CRT. It looked like a long plastic wand with a metal tip and plugged into a dvm. It had very high resistance so it could bleed down the voltage slowly.
Here's one on amazon: https://smile.amazon.com/Precision-PR-28A-Voltage-Attenuation/dp/B004PA02Q8/ref=sr_1_3?ie=UTF8&qid=1528500869&sr=8-3&keywords=high+voltage+probe+for+multimeter
As crts are rare you might find one cheap now.