1. Load your calibrated RGB composite in Photoshop
2. Duplicate the background layer called Hintergrund and make it sharp e.g. with the hochpass filter. Notice the layer settings in this screenshot.
3. Duplicate the background layer called Hintergrund AGAIN and add a layer mask on it. Click on the small white circle downside to do so
4. Start marking the regions you want to sharp with the PINSEL tool. Everything you mark is getting sharp. Look carefully
5. Use the settings shown in the screenshot to adjust your PINSEL tool for sharpening. Sharpening is like putting salt in the food. Not to much of it :-)