These are fun and really addicting to make! I love this Brea Reese Waterproof Paper- Medium Weight for making backgrounds! I've used the more expensive Yupo and various types of photo paper and this is a happy medium between the two. It's very thin but holds quite a bit of ink.
-Spray with alcohol or blending solution first for better blends.
-Drop colors of ink in various places
-Turn your paper different ways to blend colors together and use a straw to blow in different directions
-Flick alcohol or blending solution to create bubbles of lifted ink