You loose the point here. Minato didn't have to do any kind of this training because simly his Kurama helped him immediately because of these circumstances and besides, did you see Minato display any techniques while he was in nine tails mode because I certainly didn't. Since Kurama allowed him to enter BM immediately, he had no need to train. Have ever seen Naruto trained in BM? NO, he just learn it through the fighting, same goes for Minato. Don't try to ffind plot holes where there aren't any.