Hi have a slightly modified approach to Michael's above. I find that for my timing purposes, I smoke 2 hives at a time.
Before I start I smoke the first two hives that I intend to open. Then I walk away and finish setting up for 5-10 minutes. When I come back, I give the entrance a good puff of both of them again and then open the first, one quick puff across the top bars, they all retreat and I work.
When I close up the first hive, I advance to the next hive which I've already smoked. I smoke it quickly one more time and then smoke the next one that I will do, keeping ahead of myself by a hive. This way in the time it takes me to inspect the current hive, the smoke is prepping the next hive already when I get to it.
So, I am always staying ahead of myself by a hive which in my case times out wonderfully. If I get too far ahead with hives, I find it is unnecessarily disruptive to them, so my suggestion is to smoke hives in advance of yourself based on your inspection pace.