I am not going to write a long text:
Just today I finished my brandnew own brush (the 5th version) - The Camelhair Brush, similar to Painter's, for Photoshop.
I think this is getting even closer to the brushstroke of the Camelhair Brush in Corel Painter 12.
I had no time to produce a good cover for this brush - yes, there is only one brush in this download.
When you look at my preview-image, you will see strokes which are done only by one brush without changing the brush size (which is 15px)
I compared my strokes in Photoshop in every step to those I drew in Painter 12. It's the best result I was able to get so far. I hope you like it. Be sure to try it out, the preview is just a small example.
Be sure to read the text-file in the unzipped folder before sharing this brush with others.
PS: It won't work for PS Elements users.