This technique is very simple and the result will give the appearance of a wet-on-wet watercolor painting. It works well with scenics and other images which have a complete range of dark, medium and light tones in them.
Here's the original I used for this demonstration:

- Upload Image into any Image Magick
- Effects/sharpen @ 10x10
- Effects/median filter @ 5
- Output, image type = truecolor, save
- Back up to output screen
- Output, image type = grayscale, save
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| Truecolor |
Grayscale |
- Composite the two outputs (truecolor and grayscale) together, trying a variety of composite filters.
- Save the one that pleases you the most.
Below are some finished examples:
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| Difference |
Displace, twice |
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ColorDodge plus Paint (blue) |
Overlay |
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