I have been using an airbrush for about an year now for various projects and upgraded from the cheapie (try it to see if you will use it) to the Iwata HP CS Eclipse and am loving it.
Last night is used gloss varnish (Ammo by Mig) and white surface primer (Vallejo) and found both to be problematic with clogging, spattering etc and the medium residue coating the inside very quickly before cleaning.. After using the gloss in particular it was a pain to clean as the residue congealed in the bowl and I assume in the nozzle and tip. I had a similar though less drastic issue with the primer. I thinned both down to about a 3rd and added a drop or two of flow improver both vallejo brand,I got my work done but for long term use it would have required a lot of maintenance. I used the gloss varnish a couple weeks ago and had a similar issue finding it difficult to clean afterward.
Incidentally, last night I accidentally broke off the needle tip from the thread that unscrews form the special nozzle. The HP Eclipse CS has a special gold elegant nozzle and the tip does not seem to require removing the tip from the as the tool needed does not come with the kit. You get a bigger tool designed to remove the stainless housing which the gold nozzle sets inside, protrudes and easily removes from. I believe the gloss may have created a seal making removal difficult. I had a tiny tool from the cheapie airbrush that did allow me to remove the nozzle tip (when I did I found the threads dirty with red paint.) After cleaning I carefully put the tip back. I should have left well enough alone though I removed twice more last night while doing maintenance and broke it off from the thread. I used tweezers to remove the broken off thread from the inside collar of he gold nozzle housing.
I went to the store and got a replacement .35mm special gold nozzle (you get a new gold housing) that Iwata makes and also got the special silver .50mm optional nozzle as well thinking I might have better luck with varnish and primers with it.
It was frustrating enough last night that I decided to hand brush on the gloss on and not follow through on more priming as I did not want to clean the airbrush again. while moving on to another project (tanks) is when I broke the nozzle tip.
I am back in business today with my .35mm and .50mm optional nozzle and was hoping the fine fine members who have XP in this can help a fellow modeler out.