I have heard that letting it dry out and giving it 72 hours of darkness can help raise potency and the amount of resin. I have never tried it but have heard many people extolling the virtues of doing both these things.
There are no virtues in that myth. I've done it, the darkness, for 72 hours, and I've also not done it, same strain, no discernible difference. You save some money on power, but the buds don't grow any more either.
The not watering is true.... you should flush at about a week to go and that should be the last watering. In hydro grows, I cut off pumps 3 days before harvest. The dry time is reduced greatly, as is humidity in my grow tent. something I'm concerned with when near harvest.