I've used the Bilt Hamber products. The Hydrate 80 seems to do a good job of killing the rust chemically, it turns from pale purple to nearly black when it cures. Give it 2 coats as directed then maybe some stonechip over the top to protect it.
Always pour it into a separate container to use with a brush, never put the used brush nor return unused stuff into the original pot, any contamination will make it cure and will render it useless for future use.
I also use the various BH waxes, S50 and UC mainly. The UC is thin and more or less clear, it seems to penetrate well into cracks and seams though probably isn't as durable as the S50 in areas exposed to road wash (wheelarches etc). The aerosols are big and much easier to use than the open tin of UB etc., recommend the aerosols.
If you really want a bombproof job, the BH zinc primer Electrox. They say 90% zinc content. I couldn't believe the weight of the stuff, 1 Litre tin weighs nearly 3kg, that's the same as solid aluminium never mind paint. It's designed for marine use. Expensive but very effective. Available in aerosol and tin.
I get BH stuff direct from their website, free p&p over a certain amount (£50??), no commercial connection, just a happy consumer.
https://bilthamber.com/There's always good old Hammerite too, not as good as it used to be but still OK. I also use Johnstone's zinc phosphate primer, excellent product, don't bother with the cheaper "no-nonsense" alternatives from Screwfix etc, nowhere near as good.