I’m still playing around with Skitch, but so far it’s shaved at least 5 minutes off every screenshot I’ve been taking (and yes, this means new documentation is on the way for you!).
It’s a free Mac download, and well worth a try. You just click the “snap” icon on the display screen, use the crosshairs to select your capture, and you’re able to edit and annotate that screenshot within a second.
Clearing annotations to create different notes on the same screen capture is a simple button click, too.