Information about cast iron is readily available, and there are quite a few active communities full of friendly, knowledgeable people who are more than willing to share their expertise in vintage and collectible cast iron cookware.
Books
David G. Smith, known as "The Pan Man” is both a collector and dealer of cast iron cookware. He has been collecting for over 30 years, and at one point he had more than 20,000 pieces of cast iron in his collection. He has written extensively on all things cast iron. Reading his book, The Book of Griswold & Wagner: Favorite * Wapak * Sidney Hollow Ware is a great place to start.
This is a drama-free Facebook group where cast iron lovers can get help with identifying, collecting, restoring and using cast iron cookware.
Buying and Selling
Although shopping at flea markets, antique stores and auctions is limited due to the Corona virus, you can still shop online. It's tough to find a good bargain, though!
This is a Facebook group specifically for buying, selling or trading vintage cast iron cookware. All transactions are made using PayPal "Goods and Services" for the protection of the buyer and seller.