I've been airbrushing for 25+ years and do custom airbrushing on the side. I use Iwata almost exclusively except for my large guns for clear coating. I disassemble and clean my airbrushes after every session. If I reuse an airbrush during a session, I just run cleaner through it for color changes. I might take it apart if I'm doing an extreme color change like blue to yellow type of color change, but I don't often do that as I have the luxury of multiple airbrushes. I do have a Paasche VL also which I use on occasion. Same rule applies. Just remember, run cleaner till it comes through clear, and then run a little more through to be safe. Invest in a good set of cleaner brushes and lube. Makes a world of difference. Hope I've helped.
Cheers, Kevin