You just have to mix it and try it, really dont know how it will lay out with a small tip. KemFx does say their .004 can go thru a 1.4 tip, but like shine said, it really depends how much of your flake is mylar and plastic color and how much is metal. I just think of a 1.3 or 1.4 tip as trying to get as fine and smooth as a layer down. You are not looking for fine or smooth with flake, you want quantity to get a better idea of how its gonna look when you clear for that instant its wet. I guess you are considering maybe putting down possibly 6-8 coats with a 1.8, that might end up being 12-15 going on less at a time.