Phosphoric acid is good stuff. I got mine from a chemical supply house locally - full strength known as syrupy phosphoric acid - cos it is, abit. diluite 1 part acid to about 9 of water for a 10% solution. Although full strength, it won't dissolve your fingers away, but wear rubber gloves and an eye shield just in case, and wash off splashes or it stings a bit. You use the diluted stuff on rust. Many large objects can be done by turning over and over. I use one of those plastic storage boxes for that. Phosphoric acid forms the phosphate on clean ferrous (or after rust is gone). The phosphate is insoluble, so the reaction gradually slows and stops, leaving a coating which provides an excellent grip for paint - car bodies are/were phoshate dipped (unless made from zinc flashed steel). This prepares them for painting. On the zinc coated bodies they use a self etch primer.
Jenolite may have a small proportion of hydrochloric acid in it, if so, it may well keep attacking the ferous surface.
I can vouch for ACF50, if a bit expensive.However did a good job on the old landrover.
Ax's camelia oil is a mix with mineral oil (baby oil etc). Pure camelia is available on Amazon as tea tree oil (tea is a camelia) much cheaper. I usually use rapeseed oil to wipe tools, look for the yellow flower on veg oil in Tesco and check label, about £1 a litre. It's used commercialy as a specialist lubricant - presumably with adatives - but that's not needed here. Somewhere I saw Johoba oil recommended. neither are supposed to oxidise and gum up, like linseed. Veg oil is finish friendly.