I guess by charging very slowly in one direction, discharging slowly, very slowly charging in the opposite direction, slowly discharging again.
Do you have a lot of them, or just a few? What value and voltage?
Also, do you have a lab power supply higher than the rated voltage?
You need to ask why?
IF they are so degraded as to need reforming, then they are already too old.
Hey, electrolytics get replaced even if they do not need reforming, go figure, just based on age,
I guess it depends on whether you want to make commercial products, like you do, or restore historical equipment in as original a state as possible. No-one on the vintage radio sites I visit would even consider replacing electrolytic capacitors when there is a chance that reforming them is sufficient.
Not if it has been used regularly. If it was in storage for 10 years, maybe so.
My 1977 HK-430 sounds just fine, and we use it every day for hours.