Step-by-step: Take into account the nature of glass when painting a reflection
1The focal point will be a reflection of the figure, so I place it in the middle. On a separate layer I draw the perspective lines. Getting the reflection and the perspective correct can be the difference between a successful image and a failed one.
2I start on the background. I paint the girl’s reflection on a new layer, without factoring in the transparency effect. Then I select the Layer dialog and I set the blending mode to Screen, so everything that’s dark in the layer become transparent.
3Now I adjust the Opacity and Fill settings in the Layer dialog, which affect the level of reflection. Then I add weathering effects to the glass: I create a new layer and paint dirt with a light grey and a scattered brush. I depict cracks on another layer.