If you want free screencap software for Windows, CamStudio is probably best. It's not perfect but it will do what you need it to do.
I'd be willing to help, but I really should update my own Dominion video tutorial series, because it still uses iso. I also finally feel like I'm good enough to talk about the next thing I wanted to talk about in a tutorial without getting it totally wrong. I really should be doing that. Must. Find. Motivation. Hmh.
Well, that makes me think about this stuff though. If it were me making these videos, I'd be asking myself "what's the point?" What is the viewer going to take away from these videos? In one of my tutorial videos I mention that it's a good idea to read the card text and every card and understand why you would want that card in your deck. How does that card help you (and also how can it be misused)?
When I answer those questions in my mind, I categorize the cards in certain ways: Trasher, Attack, Gainer, Plus Buy, Draw, Village, Worthless. Then there are subcategories, like for Attacks you have Junkers, Discard attacks, Top-deck attacks, trashing attacks, etc. For Worthless you just have Scout
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The way I think about Dominion (which may be different than the way you all do) is a "top-down" approach. When I'm looking at a board I categorize every card like this and it gives me an idea of the landscape of the game. That's where stuff like this would fit into my mental model of the game.
It makes me think you might want to take this approach when making these videos. You can make a separate video for each card but I think there's so much repetition and not much benefit from it. I think a discussion on how to categorize the cards that is generic enough for lots of people would be helpful.