the vape button shouldn't have anything to do with the leaking, IMO. All that button is doing is firing the atty and vaporizing some juice. If anything it ought to dry it out a little bit. I didn't stick with the ego-c atties long at all though so i'm not an expert. In my experience though it was always either a cartridge end cap issue, or an airflow issue (airflow being the primary culprit). I would catch myself getting a dry hit, so i would prime the atty by drawing on the mouthpiece without pushing the button, and sometimes it would work like a charm. Or of course, i would end up with juice hands. I had the best luck (meaning fewer leaks and less dry hitting) when i took a slow light draw. I hope this helps at least a little.
as far as clearo's go, they all seem to have the potential to leak, but the vivi nova hasn't leaked a drop on me. (I've only had one for about four months though and i usually just use it at work or on the road). I've tried a few stardust style (CE2,4,etc.) clearo's that seemed ok, but i've only bought them to give to other folks. Never dedicated a whole week to one or anything.
Best of luck keeping those fingers dry!