The European cigarette consortium buys most of the Maryland that is produced in this state and they will even pay the farmer to grow it. Every year since, I have simply harvested seed from my plan tops after cutting the stalks.
WHite muslin is best.
It allopws rain to seep in as well as air and sun, but shjades the delicate transplants. I work a lot of manure into the bed of the cold frame. After the little plants get started, I thin and transplant. I usually grow enough to process about 20 pounds each year. You cut the stalks at their base, then strip the leaves from the stalks.