I've started using iMockup on my iPad for this. I've never had a good hand, so if I draw, I spend too much time worrying about those mechanics. The iPad gets me

I've started using iMockup on my iPad for this. I've never had a good hand, so if I draw, I spend too much time worrying about those mechanics. The iPad gets me away from my desktop and puts me into much the same mode as a notebook would. That said, I'm not a great designer (more of a product generalist: I can start with an idea and end with a complete product). I have to optimize for that path. :)