I usually recommend a 2nd coat because, usually, after you've 'moved back into the room', you notice some subtle 'mistakes' from having applied just one coating. A 2nd coating almost automatically gets rid of the mistakes.
I know a couple of Pros that use one coat. Then again, I know 1 or 2 that always apply 2. As for drying time, assuming all things equal, it should take the same time for the 2nd coat as it did for the 1st. 6+ hours (to the touch.)
My best to ya and hope this helps.
Jay J -Moderator
PS: I jumped in because it sounded like time was of the essence ...