Just received a package from Amazon. Literally 20 minutes ago. Another weapon in my aforementioned. Drawing gum.
So, the idea is that you use the drawing gum to create a mask. You’ll see what I mean in the illustration below.
In this, I drew the branch with leaves with the drawing gum directly onto the black card. I let it dry (well, with the help of a hairdryer: I’m not a patient man). Then I painted the entire card with diluted white gouache. Hairdryer again. Finally, I rubbed off the masking gum with a normal eraser.