[quote=@Metamore]
How exactly does this work for healing moves? I was going to have him sketch Osajyin's Synthesis.
[/quote]

I suppose... healing moves can add power back to your Pokemon instead of taking power away from the opponent. But that's a pretty cheap tactic to making the Smeargle learn a heal move. Then you can can simply switch all your pokemon into play getting them experience, because you know that he can't hurt you. 

To prevent that break in the system, I'm going to say that draining and healing moves raise the Power level of the user while also lowering the Power level of the target. Half and Half.