Is there an easier way to manually change the angle of the brush while painting other than using the popup palette? I was hoping to find something on a docker or a shortcut key but so far no luck. It would be nice to get the visual feedback as I rotate the brush to the angle I need.

any ideas?

No, that's not possible.

Unless I understood the question wrong, you can use the Rotation option for this in the brush settings. Activate one of the sensors that you want to control the brush rotation with. For example, if you use Pressure then the brush tip rotates depending on how hard you press. I would recommend Tilt direction, because it's the most intuitive option. It means that the brush tip matches angle at which you're holding your tablet pen, just like a real brush would. However, you need a tablet that supports tilt input, and most drawing tablets or screen tablet devices don't have it. The higher-end Wacom and some of the newest Huion and XP-Pen tablets support it.