I think the best resource would be yourself. Just sit down with a few cards, or maybe only one card - and twirl it in your fingers. If you can do it to a beat (could be from a song) the easier
When you have something down, can you do it with a deck in hand?
I'm assuming, by the way, you're talking about one card twirls...
G
PS: There is also a video on the media section by Richard, teaching a nice one card twirl