For what it's worth I am going to do a video soon about my experiences with Vallejo products. I hate to type so that is my alternative. Here is an excerpt from a p.m. I had with someone on a different forum that kind of roughs out what I have found pertaining to the paint, and probably covers the primer as well.
Oddly enough, as for me, the primer hasn't given me any problems. I have posted a few times on various forums (here too maybe) about my opinion concerning all of the additives and special potions one has to use to get some products to work. I find it annoying that stuff doesn't work out of the bottle. At worst a need to thin something a bit with the manufacturers own thinner should be all that's necessary. Flow enhancers, retarders, window cleaner, armadillo urine mixed with wombat saliva... just seems like a lot of hassle.
"Interesting. You have suffered the exact same situation as me. I will predict that the MM Acryl will spray fine, as mine did. I am pretty meticulous about
airbrush care, and had the same problem with the Vallejo, but not the MM Acryl. When I back flushed my new Badger 105 Patriot during the first spray job where clogging was taking place, a glob came out. (And I always spray cleaner through a new
airbrush before the first paint goes in in case there are any oils or anything present.)
As for the scum on top, let me know what you find. I am going to guess that it will be fine on top, though. I opened a bottle once and it was nice and liquidy (is that a word!?) I think the problem lies in
over mixing. Other than the paint getting a little thicker near the bottom as it gets used up, the paint worked fine
until I added an agitator. Vallejo's recommendation is to roll the bottle between your hands to mix the paint, which didn't make a lick of sense... until now. I have read that shaking acrylic paint introduces air bubbles into the paint in excess, causing minute curing of little bits of paint. It can happen to enamels as well, just not as bad. This thickens the paint a bit. I think Paul Budzig comments on this in one of his videos. I have used my Badger paint stirrer/mixer in the MM Acryl with no problems (yet). I think this works because the mixing part of the Badger mixer is inside the paint getting the thicker material off the bottom without introducing air as it is mixed. When I shake the Vallejo paint and open it, it is bubbly, as you mentioned. The MM Acryl mixed with the Badger mixer is not bubbly at all, since mixing happens below the surface.
What I think is happening is this:
1. Shaking the paint, as opposed to "rolling" the bottle introduces air into the paint, thereby causing it to thicken and/or dry prematurely
2. The agitator is loosening the "boogers" that cling to the sides and bottom of the bottle, whether it be dried paint (on the sides) or ultra thick pigment that just won't mix, on the bottom. I am thinking the latter is the real culprit.
I have a paint job on a tank coming up soon, so I will give one of the Panzer colors from the
Model Air line a try. I haven't put a, agitator in it and I am going to try the roll-between-your-hands method and see what happens.
The only other solution I can come up with is to strain the paint somehow before it is added to the cup. I am going to try and Irish-rig something using a faucet aerator. The screen in those is pretty fine, but rigid, so I think it wouldn't be too much of a hassle to make something handy."
I will let you all know when I do the video, which will be soon, so you can watch if you want.