first of all why do you want specifically 30 sec gestures? The faster you go - the harder it gets. Challenging yourself can be beneficial, but not always... It helps with finding shortcuts on building volumes, but you need to know and understand basic proportions for that. Check for example this guy gesture routine: [url=][/url]
He starts with 2 min gestures, and gradually going faster and faster. It's good cause your brain need some time to warm up, before you can go really fast. Also it is worth mentioning that gestures are not supposed to be correct or clean. It is just a fast way to capture main pose and volumes. I'd recommend not to be obsessed with clean lines, maybe try different style like dirty scribbling. As long as your scribbles gives you a clear idea of pose and balance - it is a success.
