I'm also an experienced artist and illustrator of 20+ years and I think you are doing a fine job. See if the guy that is teaching you things knows how to do a Graphite transfer using tracing paper. You trace your image of whatever you want and scribble graphite from a soft pencil on the back of the tracing paper. Then tape it to whatever you want the image on and trace over the front of the paper with your drawing and it gives you a carbon copy of your drawing on the surface you taped it too. It is so easy and cheap.
Airbrushing is a real pain, I used to do it in the 80s. T-shirts etc. Those things always clog and you end up throwing them across the room. If you can do everything with a brush, do it.
