The most bang for your buck would be to train smart and not hard, first of all you never have the same mindset against an AI like you have towards a human, meaning you don't practice strategy where a computer wont react like a human, so you can get the most out of training mode by thinking mainly about spacing and making sure you got the range down with the moves you like to use, and the more time you spend doing this the more moves you'll get use to and the ranges, and the more the barrier between you and your character breaks down, it's like you become one with your character, you are your character, and it's not a matter of thinking anymore, it's a matter of doing. Once you learn an attack it will be just an attack, and once you start using an attack, it will no longer be an attack, and then once you've mastered every aspect of the attack, it will just be an attack.
You can train several different ways, and hit confirming can be trained by setting the computer on normal or even easy and not think about beating it, but rather by focusing on confirming hits and practicing combos, spacing, zoning, mix ups, and the more you do this the more natural it will become, which I'd like to add that the highest level of skill operates on an unconscious level.
Also you can train against your own character on normal, mainly so that you can become more familiar with the move-set since you will be watching your own characters moves performed. It is important to remember that it is only an AI and not a human, so you can have at it with the same move and combos and what not to really get that muscle memory down, especially the ranges. So, basically just take it easy in training and just have fun learning however you'd like.
As for the harder difficulty settings, you can use that for reaction practice, especially for grabs, which are very important in breaking tough defenses down, and opening up more opportunities for when in actual combat, and grabs also keep your mix up game going, so keep mixing up between things like, grabs and verticals, and lows and mids. But, that really depends on the character too, like Mitsu, he really depends on the threat of that low brave edge attack, so verticals can be used much more freely, which will open up the low brave edge attack more often. And, another example would be, Maxi, he depends on momentum to keep his offense going, his offense is his defense, and he doesn't have good lows so he will rely more so on grabs to mix things up and keep his offense going. So, really you have to know your characters strengths and weaknesses, and your opponents also.
Playing to your character's strength might not always be a good idea, you might have someone who's better at zoning than your zoning character, so you will have to make them whiff then punish playing more to their weakness which is also your weakness, and same with a rushdown character against a zoner, and same thing vice versa, you will have to zone a rusher and make sure you don't whiff. There are always ways to even the odds more in your favor, and there is always a counter for everything.
