Oaking is done when the wine is completely clear and no longer throwing any lees. (You don't want yeast and other sediment on the oak). Then, it's done to taste and when it's just a little bit too much (as it will mellow in the bottle), the wine is racked off of the oak. I wouldn't like cranberry oaked, and definitely not on dark oak, but if you do that's fine.
As far as vessels, alcohol may leach things out of the plastic, so it's important to use PET bottles that are impermeable to oxygen as well as that won't leach out things from the plastic. Some plastic water bottles may be ok, many will not as I believe their recycle # is 7, and not PET bottles.