proper fork spray
What's that then. Hammerite labelled up as fork spray

(I'm scratching head like Stan Laural) MMmmm
I will be using the Eaastood Extreme when I get around to doing mine. Reason being it is an epoxy based two pack paint system, So unless they have worked out some other way of activating it or if it's a marketing ploy calling it epoxy. You activate a hardener in the can before using it. So once activated it will need to all be used.
This would be as tough if not tougher than powder coating and is probably a similar system used originally when the bike was made. If you do end up using the Two Pack epoxy resin based paint then it is vital you wear a mask as these will have nasty fumes. Even I would wear a mask with that, and I don't often abide by what it says on the can, ie health and safety.
The cheaper, quick and easy option is to use Hammerite. It's not the easiest to apply as a spray as it is rather thin and runs very easily if applied to thick. It also needs a good 24 hours before it is dry and will take more than one coat. You may get away with applying the second coat about 6 hours later. If I was to use Hammerite I would tend to go for a tin rather than spray as I think it will be easier to apply, and use a throw away brush as they a fooked afterwards unless you use Hammerite's dedicated cleaner/thinners.
Whatever you end up using remember to give the can or pot a good shake/stir first. It's also not the best time of year for applying any paints outside as the temp is cold and damp. Ideally it needs to be done in a nice warm garage/workshop. It will also a take a few weeks before it is fully cured where it will be at it's hardest resistance to the elements.
(:-})