You are referring to a method of "reforming" the dielectric of old electrolytic flash capacitors.
The method has merit but in the case of old flashes, might not be worth the trouble.
I have lots of old flashes going back 35 years, so far never a failure.
The old flashes have little value, pulling them apart is no fun and it is likely to result
in consequential damage like broken wires ( or worse a fracture that does not quite break till later)
or lost parts.
If you want to treat a capacitor gently, use a partially discharged set of batteries initially,
"blip" the on switch - off and wait a few minutes, repeat over an hour or so till the neon is on.
I never bothered to do this, but i do run all my old flashes every 3 months or so.