No-one can 'teach' or 'train' you to be a Captain. This is garbage.
Not really, you cannot teach personal qualities, help uncover them perhaps, but not teach them.
I have been in the SIM when highly regarded FOs have been in the LHS and things have started to go wrong, it is not a situation they are accustomed to, everyone looks at them for a decision, "A competent but inexperienced FO in the RHS" is the best they can hope for.
The physical transition from RHS to LHS is easy, one or two SIM sessions, the hard part is the mental transition from FO to Captain. If the basic materials, (qualities), are there than a captain can be constructed but if those materials are missing then no amount of training will help.