Here is few steps :)

1. Create transparent document (so you dont have to delete background)

2. Apply brush, for example horse head

3. Select face of the horse (not hair). You can select using Pen tool, or use Magnetic Lasso Tool    (its great for this kind of selections).

4. Press CTRL+J to cut selection on new layer in one click.

5. Hold CTRL and click on layer with face you just created to make selection.

6. Click on base layer and press CTRL+SHIFT+I to inverse the selection.

7. CTRL+J to cut hair on new layer.

8. Now you have pieces on separate layers, so delete base layer.

9. Click on first layer, hold ALT and choose H/S adjustment layer. Check "group with previous layer" and click OK.

10. Repeat the same step for second layer. Now both layers have its own H/S adjustment layer.

11. Double click on H/S layer and check colorize, from here you will find your way :)

This is most basic way, you can group curves, levels, gradient, etc and create hierarchy for each piece (face and hair).

One little trick while using Pen tool. You can convert path to normal selection by pressing CTRL+ENTER

Also you can convert normal selection to path in Path palette, "Make work path from selection" on the left of "Create new path".

For start that should be enough :)

Tihomir

Open your mind and share the knowledge!