Notes to myself: Adding gray layer for selective exposure adjustments

Rather than using a brush to work directly on the image, it is better to create a layer filled with 50% gray. To do this:

1. Open an image
2. Layer>New>Layer. Select: Mode: Overlay, and tick the box ("Fill with Overlay-neutral colour (50% gray)")
3. To make selective exposure adjustments, select Brush tool. Set Mode: Normal, Opacity 100%, Flow: 10%. Paint with Black to darken, or White to lighten.

To pin a layer to the layer directly below (so as not to affect other layers), hold down the Alt key and move cursor to the separation between the two layers. The cursor will change from hand icon to a different icon.