Your post reminded me of how I have often thought about the same thing, restoring steel with this kind of galvanized finish. I work with a galvanizer for products we fabricate at work, but the hot dip process, which is not the same process as what was used on the steel on that Gleaner.
The hot dip process has several stages, leading up to the hot dip zinc coating vat, 800 Deg F if I recall, and would surely warp the steel. It's a fascinating type of work with everything that is involved and it is for thicker steel, I forget the cut off. Gauge material we use is bought galv-annealed in sheets, to a certain gauge of thickness, might be 10 or 11. Both those cold galv sprays being aerosol cannot deliver much zinc content. We do use them and I find that although that is true, the Rustoleum when using multiple coats will protect new, or clean steel, and it will fade to a darker gray. The bright type we use when we have to weld our hinges to a hot dip zinc coated product as we have to remove it to weld the hinge leaves to the frame. Our customer seems to like it aesthetically as the cold galv spray contrasts, and I think we use cold first, then top coat it with bright as the remainder of the product is bright, so it blends better. There is no way around it. Hot dipping also requires these products to be fabricated a certain way, sizes of welds, spacing of welds and how steel parts are joined all must be coordinated to reduce "racking" distortion and or warpage. It also requires weep holes for the zinc to drain out of Even then we have to straighten the products in the finishing process.
Hot dip process is interesting as I believe there is pickling of the steel and even if the zinc coating is disturbed, it's a noble metal and kind of self heals so to speak. You may get rust, but you typically will not get heavy flaking corrosion unless it's really an adverse condition. Again, thicker steel, and depending on thickness and shape, the mil thickness of zinc that will adhere varies and typically heavier than most specifications call for. There actually is a hand held device that can measure the mil thickness of the finished product. The cold galv sprays are for repair of the hot dip process, but actually seem to do a pretty good job on raw steel, say with the mill scale cleaned off etc. I have some tube steel outside that is part of an attachment and is has not rusted at all. Brush applied is much different and is high zinc content, ASTM actually recognizes this as a form of galvanization. It's like $200 a gallon, and is the heaviest can of paint you'll ever pick up, we use it sometimes. It will turn greenish or with a different tint than the aerosol. Rustoleum makes this brush applied too. Quart was $50 last time I bought it.
The process in which is applied to the snoots and similar, is some sort of electroplating if I am correct. I do wonder if that had you one that was a bit rusty, but just the surface patina, nothing beyond that, if a piece could be re-prepared, cleaned as needed and that process then re-applied. I would suggest speaking with a galvanizer about this. The outfit we use in central NY, Hubbell Galvanizing have some very knowledgeable people on staff.