Airbrushing fine lines ???

I’m new to airbrushing, and I’m trying to get the hang of brushing very fine lines. I have a Badger 150 with three needle / nozzle combos. I’m spraying Model Master flat enamels, which I thin at the recommended ratio of 3:1. However, I notice that when I use the fine needle / nozzle combo, I cannot brush nearly as fine a line as I know the unit is capable of. It almost seems like I can brush a finer line with the medium needle, and I know that’s not right. My question is, should I thin the paint a little more when I’m using the fine needle?
Any suggestions would be appreciated.
Thanks!
John

I use the same airbrush/paint combo. I thin the paint to almost 50:50, and spray at about 5-7 psi. with the fine needle. I used it on my signature pic, and I outlined the mottling, & then filled it in. Hpoe this helps !

low pressure and close distance will help a lot.