So the structure in our team is that several managers work under a senior manager, and each manager is in charge of one or two analysts. I am an analyst under Manager A, but sometimes Manager B comes to borrow me to dump some of her jobs to me, and my manager agrees because he can't generate enough work for me. She also lets the senior manager know so she really isn't going to take my credit for this (she did on some side jobs she asked me to help, but that's another matter).
The problem is that, for some reason, she is not willing to give me any meaningful training on the jobs she hands over to me. Our team is quite technical (within a bank) and many business logics are not well documented. Training by seniors is almost the only way to learn. The only form of training she gives me is allowing me to attend some meetings on which some aspects of this job are discussed. For example, members from her team brief on the findings, or discussion on some technical nuances.
Never did she give me proper individual training on the backgrounds and how to actually do the job. When I ask her questions, she would give cursory answers and ask me join one of those meetings.
Despite all this, she would brag to the senior manager how she spent time training on me. And this makes the senior manager think I already have a good command of the job but actually I do not. (So far I don't really need to do the job because it's done by her analyst. I'm only trained as sort of a backup.)
What complicates things more is that I have jobs from my own manager to focus on. So I can't spend too much time trying to figure out the job myself. I can't ask the analysts working for her either, because it seems that she already told them to direct all questions to her.
What can I do about this? I want clear instructions and guidance on where to start; what I need to know.