Here's how I do the roan, not sure if it's the correct way lol

I duplicate the horse layer, then make it white, basically so that the horse looks like a normal light grey horse. I duplicate this grey horse layer too.

First I work on one of these white layers, I make the other not visible. I grab a brush that has the form of small scattered spots, set the opacity to pressure sensitivity, and start erasing from this white layer until the horse looks roany. I completely erase the head and legs so that the real color of the horse shows.

Then I make this layer not visible and do the same thing to the other white layer too. When both are individually made, I make them both visible and play with the opacity, contrast, brightness settings, also I erase more if needed.

When the roan looks just about right, I grab a weak smudge tool and smudge the roan into the muscle lines so the little white dots look like hair rather than just white splatter all over the horse. I follow the muscles of the horse, so basically repeat the smudge step from the body prep until the roan looks fine.

Edti: For the fading about us and text avis:

When I have the bio image, before adding text, I merge the whole image together (but make sure to save the file with all the layers intact too!), grab an eraser of whatever form I want and erase back from the bottom. then add the text and save it as PNG.

Text avis: Just load up an empty document with no background color, add the text you want, then save it as PNG.

The key to transparency is the PNG file format as this one keeps the "emptiness" of the image. Other formats just make whatever empty space white.