Duplicate image. Apply Image>Adjustment>Invert on top layer. Use Color Dodge blending option. You’ll have an almost white image but don’t worry it’s still there. Apply Filter>Gaussian Blur of about 4. You’ll get outline. Convert to grayscale to simulate a sketch to guide your brush strokes.

Erase extraneous lines We’ll do selective coloring so the outcome is like a vignette. Convert back to RGB. Using Art history brush tool, select appropriate brush tip (watercolor 1) & size. Turn brush dynamics on and use a graphic tablet. At this point everything is blotchy and the colors are muddy.

Change tool to History brush, normal blend mode, low opacity and start to put back some of the definition on the image. On areas where it is dark, change blending mode to screen and remove some of the color. Where you need the areas to be dark, change blending mode to multiply and saturate image. Change the opacity for effective use of the brush.

This last step is optional. Instead of running unsharp mask I use this method to bring up sharpness plus it gives some texture.

Duplicate the image. Set top layer to Filter>Stylize>Emboss. height - 6 amount –76%, angle 74deg, opacity to 25%.

And if you are so inclined put down your signature on another layer. Flatten.