PostworkShop allows you to paint your own painting with a little help: using a Reference Image or a Cloning Source.
Open PostworkShop and load the image you want to be your reference image. Right-click on the Default Layer and select Edit. PostworkShop automatically switches to the Paint Module. Open the Settings window and select the Canvas to be a Color instead of the Original Image - as explained in 4.7.1 Painting on a canvas without reference Image. Open the Settings window and add the Reference Image visual guide. The reference image will show up in the viewport (Style Editor will be automatically connected even if you have not done it). Adjust the guide’s opacity by moving the slider and start painting.In this tutorial we selected a Colored Reference Image but you can also chose to view only the Outlines or the Grayscale. Select the brushes you want to use and start painting/drawing. (We chose Paint Brush 1 family) . Select the brush color and start painting. You can check how your painting/drawing is changing by switching back to the Compositing view (as shown below) or simply deactivating the Reference Image: set the Visual Guides to OFF.
Switch OFF the Visual guides to see the result of your work.

If you do not like the result, you can use the trashbin to delete the last strokes. Press the button as many times as you made changes in the settings, to delete all the strokes, modifications you have made in the Paint Module to your image.