Smoking brisket on gas grill?

There are V shaped smoker boxes you can purchase that will fit in between the gas burners which will produce enough smoke to be able to add flavor to your food, or you could use the soaked wood chips like you were talking about, wrapped in foil with a few holes poked in it. This all needs to be accomplished on a gas grill large enough to utilize indirect heat.

Should I wrap in foil to help keep moist? Or just on girll and add butter or whatever every hour?

I just hate opening lid to lose heat

you are probably better off with a fancy marinade / preparation and low heat oven IMO

good luck though