In the beginning of the manga All might had to train deku for him to able to hold the OFA. However in the recent chapter ( I don't remember when) we saw the former user barely holding to their live giving the power to another one, so I guess they were already trained (or still in training) and their body were able to hold the power. So I was wondering did All might by being quirkless and having for goal to defeat AFO, trained so much that he gave a really a lot of power to OFA.

I can also had that the other user had Quirk (I don't remember if it was everyone except for all might) so they might have used OFA as a power up while depending on their original Quirk. (Weaker point) The body transformation of All might while using the power. ( His powerless appearance is the same as he was before getting the power. )