For first, apply the image a Random Painter (we leave the default settings without any change for simplicity). Then, switch to the Style Editor and add the Bitmap Editor filter.  It is possible to insert the Bitmap Editor filter node in the Style Editor as any other Style/filter.
There are 4 ways to do it:
- Double-click or drag and drop the Bitmap Editor filter from Building Blocks/Editors into the Style Editor workspace.
- Right-click on the filter/style you want to modify and click Edit.
- Right-clicking on the filter/style you want to modify and selecting Bitmap Editor as shown below.
- Double-click the filter you want to edit and select Edit the Image:
The Bitmap Editor filter will be inserted and linked to the previous Random Painter and to the result Layer#1.
It appears clearly that the greatest function of the Style Editor in relation of the Paint Module is that you can choose your preferred Cloning source and Reference image. In fact, you have the option to connect any other filter/style without it being the default one.
Example: choose Random Painter as the Bitmap Editor’s input which has already been applied to your image and make the Cloning source the Random Painter modified image. Link the Image’s output pin to the Reference image input pin. The more complex your graph is the more option you have to connect different pins as reference sources.
Note: it is not mandatory that you connect all the input pins of the Bitmap Editor Filter - except for the Input pin. In fact, when switching to the Paint module and enabling in the Settings window any visual guide, these will be automatically connected to the Bitmap Editor filter. However, this does not guarantee that the pins that will be conected will be those you   actually want to be connected. By default, the Cloning source will be linked to the previous filter's output pin, and the Reference image to the Image source's output pin.
Now that we connected the pins to the desired filters, images, to be able to modify the Random Painter style, you need to switch to the Paint Module. Double-click the Bitmap Editor filter.

We will use the Paint Module to fill the lower right corner and to paint with smaller brushes the flower, while the green background will be painted with bigger brushes.

In the Visual Guides settings, as we have already connected the Image source as our Reference Image, click the Reference Image and select to view it Colored. Adjust its opacity to the opacity level you prefer.
Then select a bigger brush size to paint the background and the right corner, then chose smaller brushes to paint the pink flower.

Once you finished, save your work, or go back to the Compositing/Style Editor to continue working on your image.