8-10 square metres per litre.
Etchweld is the best product to cover a continuous galvanized area. In situations where a galvanized surface has rusted in patches, remove rust with Deox-GEL and patch just these areas with Electrox Zinc Rich Primer
Yes, use 10% xylene to thin the Electrox.
No, as this product must contact bare steel, and hydrate 80 cures as a primer, covering the bare steel. Use Epoxy-Mastic over hydrate 80.
1.6mm-2.0mm is best.