It's specially formulated for non-ferrous metals and brushes on really easily and you can wash your brushes in water. A 250 ml tin lasts for years and is a real bargain.
The coverage on figures is excellent, producing a thin coat that easily accepts a thin undercoat without obscuring any detail. Yes I both prime and undercoat. I've never had any problems with paint chipping, flaking or rubbing off.
I was intrigued why it was called a special metals primer. I found out that the main reason is that lead, tin and copper have different surface properties from iron and steel such that they don't accept paint very well.
According to International Paints the Special Metals Primer "has an adhesion promoter and pre-treatment within in to allow it to be applied to these metal types". That put me off regular primers like car primers and explains why I've not been disappointed in over ten years of use.
Try it and let me know how you get on. You might be surprised.