I’ve just found a free programme which lets you draw images and text, a bit like Illustrator, which I haven’t used, called Inkscape.
I experimented with a robin seeing as that was pretty fresh in my mind!
That got me thinking there must be some good free drawing apps for my phone & I found Drawcast. You have to use your finger so it’s less accurate than a mouse, but I think it should produce some good effects. It’ll also be good for times when pen & paper is less easy eg at work or on the tube.