For the thumbnails I just stay at a 50% zoom sometimes even 25%, and focus mainly on shapes, letting the thumbnails take its own direction.
The brush I used is one I made for myself, but you can find similar brushes in Jaimie Jones Brush Pack. I used to download everyone's brushes, but now I decided to just delete everything and only use the ones I make up. Because you know best what kind of brush you need.
Hope that helps!