With oils, pastels or acrylics, you can take a soft dry brush and lightly go over a misty area with gentle circular strokes to soften the outlines, obscure details and blend the colors. Remember that fog Lightens, Reduces Contrast, Cools and Mutes Colors, Eliminates Detail, Softens Edges and Shortens Visibility, flattens the picture plane. You can turn any landscape misty with some practice.