This achievement is made much easier if you have a turbo controller. If you have one (like the Hori pad, etc.) then the following setup will make this achievement painless:
Set the game to 7 points and only 1 match and save these settings.
At the main menu go to exhibition and pick the easiest setting.
Pick any player for your player (pick someone you don't have all the outfits for) and pick Luc for the computer
Start the match and set "A" to turbo on the slowest setting (For the Hori pad, hold "A" then press turbo twice, then let go of "A". *not sure what the procedure is for other controllers)
That's it. If you watch for a bit, you will notice your character will more than likely win almost all matches (except Mark, he's a little wild and may lose more but no matter, the ball is still moving and counting progress.) It'll reload and keep going over and over again until you're done.
I do recommend changing out characters every couple hours if you still need the outfits, because after a character has won 22 matches, all of their outfits will unlock. Rinse and repeat!
Update: I just unlocked all outfits using this method, so I can verify it works! Every couple hours or so, go back to character select and see if you have all outfits, if you do, move on to the next person. If not, select that same character and let it run for a little while longer and check again. Good luck!