Lightroom 5 beta video 4 – Radial Filter Tool
Ctrl + double click to create a full frame filter.
Shift + drag to create a circle.
Alt + drag to start drawing the filter where you first click at.
Ctrl + Alt click inside an existing filter to duplice that filter.
Also a look at the grid and guide overlays.
View -> Loup Overlay -> Grid
View -> Loup Overlay -> Guides