I finished some of these doodles a few days ago but I forgot to take photos of them and share (bad girl) Better late than never!
I created these doodles by first dropping random coloured artists inks onto cardstock and letting them bleed together naturally and flow on the surface, if a pattern started to form I would blast them with my heat gun to force the pattern to stay that way rather than let them blend in further.
See pic below to see what I mean:
Once the inks where dry I used a black pen to outline the distinct patterns within the inky background like so:
This then formed the basics of my doodle patterns which I then filled in using a black drawing pen and a white gel pen to add highlights and freeform tangle style patterns.
This technique is good if you find yourself stuck and dont know how to begin making a doodle because the patterns in the ink colours do it for you intuitively.
You can see all my doodles I did below, I love how the backgrounds pop due to the bright colours. (click pics if you need a closer look)