It'll only clear itself if the bag is able to completely contour to the bottle's shape. The way he has it now, it looks like the bag won't be completely sucked in when he inhales, and so it's possible that smoke would be left over.

Waiting for the smoke to slowly make its way out the top would be a pain in the ass, and while waiting for it a lot of the smoke could condense and coat the bottle.

If the bag is big enough, yes, he won't have any trouble at all as is. Otherwise, he'll either need a bigger bag or a carb.