Is there any trick/short cut to rotate brushes on the fly, like on the keyboard? Instead of going to the brush palette to change it everytime?

Oops, wrong section. Mods, please move this to Digital Arts, Retouching section?

Nice links. Unfortunately, rotating the brush is not there.

I saw a youtube video, a digital artist was brushing hair with rotating the brush on the fly. Like brush one stroke in one angle, then next stroke brush will be at another angle without open the brush palette setting.

Maybe they had the option Direction on in the brush panel..Could be wrong

In the brush panel if you click on the flip x and flip y axis in the main panel and the inside panel, it should do the with each and every stroke, not sure if that is the answer your looking for. You can do a lot inside the brush panel, it is very worth the time to learn.

All the best...

There are also individual check boxes located within the "Brush Panel" that say things like "Jitter" and "Rotation" for different brush attributes. 

If you are looking for how a brush can look different during different key strokes or within the same keystrokes...then this "Brush Panel Icon"  in the  "Main Top Menu"  has some options you can program in... and then save that special brush setting as a future "Brush Preset".  This way you will always have that special type of brush available to use after you get it to operate how you like.

There is a very large range of brush Actions and Looks and Settings that are available.  BUT, Its not always totally intuitive what each setting will look like visually with that one brush you have... SO, experimentation and detailed testing are the order of the day!!!   Sometimes it can take quite a while to get the brush to look and behave exactly like you desire it to! 

So, Google up a tutorial using a phrase like  "Photoshop CC Brush Panel".  I have seen some nice explanations of what all the very many settings can do.  Its Very Powerful.  God Speed!

I said "palette" above, I actually meant panel.

Thanks everybody. I am aware that can be done in the panel as I stated earlier. That's why I wonder if it could be done with a shorter cuts thru the keyboard, thus saving steps x strokes = time.

I think LeonardG could be right. The video I saw was a damn good artist, I'm sure those folks have expensive tablet. Why the hell I assume he was using a mouse? Duh!? Pot should never be legal in my state.

https://www.youtube.com/watch?v=nC-yC-uOaBA

brushing at 13:34, it has to be a tablet with fancy pen?!

No keyboard shortcuts. But here's a workaround:

Take your brush and save it as a brush preset. Then rotate your brush by 10 degrees and save it AGAIN as a new brush preset (uncheck the "Capture Brush Size in Preset" box). Add another 10 degrees, save again,....
So at 10 degrees change, that's 18 brushes you need to save to get 180 degrees.

You can then use the shortcuts for "select previous brush" and "select next brush": Keyboard shortcuts are , and .

Quite a bit of setup work, but worthwhile. If you're working from a tablet, you could map the "," and "." keys to the Wacom's touch strip. Works a treat.