hi, im a Hot dip Galvanized inspector, currently working on a HDG facility, if i can help with something, ill be glad to help.
if you need masking for not galvanizing components, i would use Galvastop by puma chemicals, this is one of the best product out there.
there are other products that you can use, for example : caulk or silicone... they work great, when we dont have Galvastop, there is always cheap caulk or silicone that we use on out selective galvanizing process
not every galvanizing facility uses Lead.. also the white coat you see on older galvanized stuff is not leat oxide.. its zinc hydroxide.. you can clean this with vinegar and scrubbing.
in the facility i work for, we use Zinc SHG, Bismut and Aluminium.
also HDG must be 98% zinc in the kettle, other metals are restricted by ASTM 123...