Maybe I am just slow on the uptake, but it just occured to me the use the old bent-tip Tamiya airbrush needle, reversed to blunt end first, to hold the trigger assembly in place while I clean the brush and the 'good' needle.

Tamiya airbrushes, with the needle going through the trigger assembly, can be a bit fiddly to put back together if the trigger pops out during cleaning and I got tired of using tape as Tamiya recommends.

Then I saw the old needle in the parts box.

I reversed it and put it into the brush, blunt end first, poked my hand on the protruding sharp but bent tip, cut that off with the wire snips, then slid it in far enough to hold the trigger assembly but not so far as to interfere with cleaning into the paint channel area, tightened the nut, and used that to hold the trigger in place while cleaning.

I hear that the Tamiya gun is an Iwata clone, or even an Iwata with the tamiya logo stamped on it. So this ought to work for those as well.

Even if you do not have a spare bent needle, a bit of brass rod will do the trick as well.

Or maybe you have all been doing this all along...

Mike