This one is beyond simple if you have two controllers. Just jump into a painting and join in with your second controller. It doesn't even have to be logged into a gamertag or anything. Place the dummy character up against a wall and keep tapping X to pummel the snot outta it with your main. It dies/vanishes about every 80 smacks, so just push A on the 2nd controller to respawn it when this happens.
Since there is apparently no online Kung Foot or painting play, you're out of luck if you don't have 2 controllers. There's always the option of a walmart *rental* lol.
Edit: If someone can test it out I think maybe punching your 'creatures' that you get from scratch off tickets might work. I just checked and you can punch them but I don't have a dummy account with any creatures unlocked to test this.