I have done a lot of painting with Hammerite, both from rattlecan and from a paint gun. This includes prep, wipe-down with solvent, primer, and paint, all at temperatures above 70F. While the parts sure look nice when they're done, I have been frustrated by chipping and scrapes. Maybe it's the over-the-counter formulation, or maybe the glass particles in the paint start looking good before the paint is thick enough to be durable. Whatever it is, if I just look at the parts they scratch.
Wrinkle paint is a completely different beast. It's tough. To get the right finish, you need to bake the parts in an oven. I've used a heat gun with good results. Nevertheless, it is a challenge to get an even, uniform finish with wrinkle paint. It is best to practice beforehand. Can really look nice when done right. Won't scratch!
My favorite paint for bare steel or iron is engine enamel, cured with a heat gun. That stuff makes a thick coat that is hard and durable. I painted a lathe headstock with it and was pleased with the result. I've also painted engines with it, of course. It's tough enough for tools.