I've used several brands of airbrush and spray-can primers, having found each to have strong pros and cons. This one seems to be middle of the road, a good general purpose primer. Here are some of the ones I've tried and my observations.
First I want to start off and say that I HATE Vallejo's regular Model Colour Primer. That stuff barely sticks to anything and comes off in big flakes from even 'easy-to-adhere' surfaces. Forget about sanding it!
By contrast Vallejo's Mecha primer is a lot better, it goes on smooth and has better adhesion. It doesn't clog my airbrush and has reasonable, but not the best durability. It can be sanded with fine grit, but anything below 400 grit and the large grains risk shredding the rubberized surface. Give it time to cure and use a light touch though, and it's possible. Curing (not handling) time is fairly long compared to some other primers. Badger Stynylrez for example cures so fast it's sandable in under half an hour, and as little as 5-10 minutes with a blow-drier to kickstart the process. For Mecha primer you'll have to be a little more patient, as it remains a bit rubbery after drying.
Badger Stynylrez is a primer I have mixed feelings about. On one hand It has the highest durability and best sandability of any airbrush primer I've used. On the flip side, I've found that the adhesion of airbrushed paints to this primer can be a little lower than expected, with fingernail damage becoming more common while working on a model and before adding a protective topcoat. It's also very difficult to get at a reasonable price here in Canada, and amazon is full of reviews from people who have received bottles of congealed gunk. There seem to be quality control issues and exposure to low and high heat during shipping can ruin bottles. It is common for the bottle to develop many clumps over time. It will clog your airbrush during use, and ruin any brush you use and don't wash immediately. It kind of lives up to the brands namesake, tough as nails but ornery as s**t.
I've tried AK's primer and microfiller too, but was disappointed. The surface is somewhat matt and rubbery, not giving the best sanding results and taking a long time to dry. It's still decent primer but the larger issue for me is that after spraying even a ml or so to coat a single mini, my ENTIRE apartment smelled so strongly of nail-polish that I had to wear a respirator for several hours. It also doesn't do a great job of 'microfilling', at least not any better than any of the acrylic primers I've tried, which can be a pro or a con.
For rattle-cans I've tried Grey sandable automotive primer, White Army Painter Primer, and White Tamiya Fine Surface Primer.
The sandable automotive primer was great until local shops stopped carrying the brand I was using. I tried other brands afterwards and had poor results with it. If you can get a good automotive primer that would be my first pick for rattle-cans, hands down!
Army painter sprayed on nicely, but I found the white needed several coats and had a chalky finish. It worked though, no doubt, and has pretty good adhesion.
Tamiya was my favourite of the model primer rattle cans, with good application and great adhesion on various 3D printed plastics, including smoothed ASA/ABS. It is unfortunately more expensive than the other cans.
The downsides to rattle cans are the higher cost, outdoor requirement, and the fact that they cannot be used in winter, so an alternate primer is required for part of the year.
My conclusions; Vallejo Mecha primer is a good middle of the road product, with no huge drawbacks, but is not the best in any category either. If it had better sandability it would be my first pick. I'm not sure yet if I'll go to the trouble of stocking stynylrez again with all the issues I had, and will probably favor keeping some tamiya surface primer around for the jobs that need more adhesion (like pla/abs).
French