One, it is a siphon-feed airbrush and needs pressures around 20 to pick up paint consistantly, if you want lower pressures then you need a gravity-feed airbrush like the 100LG, Omni 4000, etc.
Two, the fine needle was designed to be used for a paint medium that has very fine pigments and most modeling paints do not fall into that category.
You can thin enamels to water consistancy and still not get the results you want as the pigments are too large for a fine nozzle/needle combo.
Remember that nozzle sizes and needle sizes are designed for a certain medium and modeling paints work best with a medium tip, although you can get away with the fine tip somewhat it is much trickier.
“Wisdom is the right use of knowledge. To know is not
to be wise. Many men know a great deal, and are all the greater fools
for it. There is no fool so great a fool as a knowing fool. But to know
how to use knowledge is to have wisdom. " Charles Spurgeon