Making a video of your game

My games play at 800x600 and my intention is to try selling them on steam. I’m trying to build a nice video but I’m failing. I’ve tried OBS (Open Broadcast Software) which captures the video and sound if the game is run in a window but it looks quite fuzzy (I suspect scaling issues). It’s also a pain it won’t capture the game as it’s playing on the full screen. I’ve also tried shadowplay but I just get a blank screen though the sound is working.

How do you guys capture video? and what do you edit it with once you have some video? I’d like to be able to scale it down in size so it’s a smaller file and is easier to display on the store front (assuming I ever get that far).