Raise ability by performing/practicing?

I suck at the ability minigame, so I’m looking at another way to raise my band’s skill.
I would like to mod it so that each performance and/or practice session raises the bandmembers’ ability by a little (a little higher than the decay), but I can’t figure out how to do this.
Is it possible, and can someone tell me how to do it?

Yeah I need help with that as well, i can’t find a way to mod the saved game xml file.