I used the old high VOC Hammerite (smooth version) on a motorbike frame. It looked raelly great, but after about 3 months there were some stone chips. It carefully touched them up but the problem persisted with ever more chips out of the paint. The stuff is really brittle and frankly not fit for much more than painting tools or metal gates.
The new low VOC takes years to dry and seems ok on my wife's Panda back axle, but it brush marks badly needing three cost for a good coverage. For work involved I would do the next one with spray primer and brush on polyurethane gloss.