Even though it is an automotive primer it works amazingly on both plastic and metal models. It goes on smooth and thin. I have yet to notice any detail obscurement from spraying too thick.
The only downside this paint has is that it does not exactly match Chaos Black. It is just a tad bit lighter. This hasn't been a problem for me though. Even when I dry-brush over it with another color and leave the primer as the black basecoat it looks just fine.
If you are painting a large number of models of tanks and are going to be using black primer it is well worth it for you to pick a can up and do a test on a few old models you have laying around since this primer is about $10 cheaper than GW Chaos Black primer. I pick mine up at Wal-Mart, Lowes, or Home Depot. It should be available pretty much anywhere in the US. Not sure if they have this stuff in the UK or not.