I dismiss them to bump up my clan's average level, then recruit new ones.

If I really want to level up my scrubs, I send them into battle and have them sit there and use potions on my highest level characters. For Nu Mou and Moogles, I can have them cast Quick/Smile on Montie, who smiles them back, so they can quick/smile him, and so on. It's pretty mind-numbing, but it produces results.