You can change the needle, ( without removing the trigger ) in
a VL airbrush, and probably any other brand, by doing the
1, remove the head assembly
2, loosen the needle locknut at the rear of brush
3, take the needle you are NOT going to install and push
it backwards into the locknut, pushing the needle in the
brush forward. Hold light pressure on the trigger and push
the needle out of the brush.
4, take the needle you are going to install and push the backend
into the front of the brush. Hold light pressure on the trigger
and push the needle in until the other needle falls out of the
backend of the brush.
5, replace head assembly an tighten locknut, your done.