I do not beleve VPD has anything to do with drying, only living plants..........and it really isn't that critical for your average home gardener.
Worry more about learning the basics like watering and feeding and observing your plants and tuning in to them and this will pay bigger rewards than most anything else.
VPD is more for commercial growers trying to maximise profit, not the average home grower trying to get some hand made goodies.