I don't have any experience in sales, but I'm eager to learn. Any advice on which content I should consume in this area?
I always recommend people new to sales/marketing read "Crossing the Chasm", it has been continually updated and is essentially how to sell new technology products to the general market. While you aren't selling a product in the traditional sense, you are selling a dynamic product which is you and your skills. So while there will be parts of the book that seem not as relevant it will still help you get a broad understanding of how to market/sell your services. And think of the product as yourself, that's what you are selling when you are a one person dev shop.
I am happy to share my experiences if you have specific questions, I struggled starting my first agency as I didn't have anyone to ask questions to and just had to screw up a ton to figured out what to do. I was super lucky many many times that I didn't tank that business, but was within days of doing so multiple times.
Also talk to your primary and ask them for recommendations to clients they turned down for being outside their target demographic. Also make sure you get your primary to provide you a written recommendation as early as you can in these projects. I know this sounds odd but all software projects will have struggles and I always found getting recommendations early meant I got much better ones then when schedule changed etc. Even if we were not at fault the recommendation would be less then I would have liked when I waited too long.
Last comment. As for your plan the one key thing to identify is your ideal client type, size etc. It is less about Technology and more about client demographics. This helps you create a target client list and start hammering the ground finding contacts in to them.