David Chartier details his workflow for iOS screencasts and GIF generation. I have exactly the same setup, especially when it comes to GIFs:
After you open or drag a video into GIF Brewery, you can select a small portion of the timeline to GIF; it’s really pretty simple. You have some control over how colors are squashed for the GIF format (it only handles 256 colors, so you might have to fiddle a bit here) and the GIF frame rate. You also get an overall file size meter and warning if you get close to or over 1MB; a number of of services (like Tumblr) and web hosts seem to not like anything over that, so GIFer beware.
In addition to ScreenFlow, I would also suggest ffmpeg2theora, a simple converter for Ogg Theora video files. It’s a command line utility, and I use it every time I want to embed an HTML5 video on MacStories with MP4 and Ogg source files.
Obviously, Reflector is still the must-have for iOS screencasts.