Now I understand what you need. Have you tried Puppet warp, warp and the liquify filter? I know that will all be time consuming, too, but if you are doing a large surface it might be worth a shot.
The other thing you might try, as Dennis mentioned, run multiple brushes... I took your image, made 3 brushes and ran each on a copy of the path. I didn't do a good job, but with a little effort it might work I varied the spacing on the brushes to make it more random. I used to do 3D texturing, but it was about 20 years ago! Another thing to add in the brushes which I did not... is texture.
