I did these at the Austin airport in my small Moleskine watercolor journal, while waiting for our flight home. I used a Uniball Vision Elite pen, not my usual Prismacolor fineliner. I found it very fluid to use, which I think helped loosen my style (something I'm always aiming for). I bought this pen for our trip to China last year because it was advertised as "not exploding on airplanes." I don't know if it's waterproof ink, but will check it out.