You are right and it has been well covered. However, I have searched and found no definitive answer, only lots of opinions.
Those who have done it swear that the only way to ensure it is done correctly is to do it yourself and there is at least a couple of decent Youtube video showing how.
However, ideally you need access to somewhere where it can dry really thoroughly between treatments = really big garage, preferably with heating, and a 2 or 4 post lift to get proper access. There are guys who will do this on their drive and fair play to them, but that would be a painful process I would be willing to pay to avoid.
There are those that swear by Dinitrol and those who use waxoil, there are those who dilute waxoil to give better penetration inside the chassis and those who don't.
Before n After use a different product which the owner makes huge claims for and which should come with a decent guarantee.
https://before-n-after.co.uk/ However, he is pricey and seems to do the whole process in a day, so I would want to see his drying facilities as it needs to be completely dry after pressure washing. He will not give that guarantee if your LR had rust beforehand, whereas dinitrol treatments stabilise any remaining rust (within reason) and do come with a guarantee. Some members have also had an issue with the owner personally, but that should not affect the quality of the service he provides. Flatdog seem to do a decent dinitrol service done over a few days at a sensible price; they will do free pre-assessments and I've not heard any bad things about them. Once the weather warms up I will be taking my D2 to one or the other. Maybe my son will take his D90 to the other one so we can compare quality and experience.