I' ve had stuff hot zinc sprayed, and is ideal for heavy lumps. We used it on wiches for fishing boats and the loading cranes. Once the rust has been grit blasted off(rather severely), the hot zinc powder is melted as it's sprayed. We also do it with nickel now for building up the wear pads on oil drilling tools.
Due to the grit blasting, thin components are not best suited to this. The finish can be as rough as hot dip galvanising, and usually granular - which is an ideal key for thick paint.
Hot dip galvanising can have drawbacks on complicated sections. Box sections can't be effectively cleaned, and if rusty the zinc will just avoid it. Also air pockets form and usually in the worst places - corners and welds. As it is a hot process, distortion is a problem unless you make a frame jig.
The Electroplaters I've been to offer tin-zinc which gives a bright finish. The tin acts to make the zinc less available to atmospheric corrosion,so remains brighter and lasts longer. This method has problems on concave or box sections, as the charged particles of zinc are attracted to the nearest object - so edges get a thicker coat, and hollows and corners get the mimimim. Passivation is important as it again increases the resistance to oxidisation.
Ideally I'd love it to be grit blasted, then tin-zinc electroplate, and chromate passivated. Sprayed externally with an etch primer and 2 pack colour, and internally a coat of black waxoyl. - Should last for 100 years !