Haven't played the PSP version, but if it works the same as the original game that's unnecessary.
Move the master character into position, bring their created character out to stand beside them, but don't use an action. Attack with the main, hopefully getting the combo. You can then undo the move of character you're levelling since they haven't used an action yet, returning them to base (or their previous position if they were already in play) and they keep the stats gained regardless.
Because you undid the move, this character still hasn't had their turn though, so you can repeat this trying to get combos with as many of your other characters as possible, and still undo the character's move if you want them safe at the end of the turn.
#3781975, By Stoatboy disgaea on PSP
Stoatboy 88 posts
Seen 5 hours ago
Registered 11 years ago