First of all, please read these instructions from Linmarie.
Although spray-cans produce the best results, I ttried the acrylic method. I used string soaked in watery acrylic paint. I then used coloured pencils and fineliners.
As an exercise in using one’s imagination I thoroughly recommend it – thank you Lynmarie.
Here is how my picture looked before I set to work on it with the coloured pencils: