If I may,
I've used both Vallejo and AK varnishes through my airbrushes, usually on a low pressure to mist over powders and found them to be just as resilient. I was put off using Humbrol varnish from the bottle when I found very inconsistent results a few years ago, even the model shop who stocked it put a notice below the bottles warning of such problems. I have however had good results from the spray can as per Rob.
I have also had really good results from the Army Painter Anti Shine Matt Varnish as used by wargamers on their "toy soldiers" .