Credit for this tip goes to Don’s Airbrush Tips , specifically the section on airbrush ergonomics.
This first tips deals with an issue I notice in using the airbrush for long periods of time. Since the airbrush made of a shiny metal, I tend to grip it tighter then I should. After a while this tends to cause my hand to cramp up.
Using this finger wrap (via my wife).

You then attach it to the sides of the airbrush where you grip it. I decided to also tape along the sides as that’s where I normally grip it.

The result looks weird but definitely a much more comfortable grip. The difference is night and day and is well worth a try.

His second tip on using a little plastic circle to increase the grip and size of the trigger is worth trying as well.