It’s important to add that the Slow-Dri being mentioned is the Additive, not the Medium, both of which exist in the Liquitex lineup. Additionally, Flow-Aid is a concentrate. It’s meant to be diluted 1:20 with water or thinner right out of the bottle. So, it’s not 5% to an airbrush cup, it’s 5% to a thinner mix which you’ll then thin your paint with as normal.