There seems to be something funny going on when trying to trade boffs. They just disappear into thin air.
I've send several boffs to a fleet mate of mine so that he could train them in Gravity Well 3 but the moment the transaction was made the boffs are nowhere to be found.
I asked him to send some a couple of cheap boffs my way to see what would happen and the same thing.
So it's impossible to use the captain training for skills like Gravity Well 3, etc.