well either way, any person is better than none, at least they DI so you can practice combos.
lol, that's how i trained some of the crew I'm in right now, they used to suck badly but i just played them to practice and they eventually got good (not really)
Another thing i would suggest is the level of your computers. I personally practice on Level 1's, to practice combos since higher levels tend to be random as hell, and other various reasons.
Also, if you want to learn how to chain grab (i saw the clip near the end), go to training mode, and set the computer to "avoid." The computer will now DI your upthrows, making you chase after him. I'm not sure if you know how to jump cancel grab, but you will need to do this in order to grab the opponent. (you should get used to pretty much always jump cancel grabbing in game). [to jump cancel grab, press UP then immediately press Z. If you do this right, you will notice fox's grab to be less laggier. This may take a few tries, and you might accidentally jump and do an attack, so if that happens you're doing it too slow.]