rust prevention...
I have had good results from:
wire brush loose / heavy rust first!
Kurust ... converts existing rust residue to an inert substance ... i applied it to parts of my classic BL Barge in 1994 and it started to bubble again in 2004 ... so i thought that was really impressive! It also acts as a primer ... however i always apply primer as well ... belt n braces!!
Waxoyl ... contrary to popular belief it is for HIDDEN areas like box sections ( injection tool required) and internal or protected areas . It is not designed to be in 'splash' zones or else it will wash off ... and yes it remains slighlty liquid so that it can 'creep' to cover an area if need-be.
PS if you are intending to inject it, may i suggest that you buy 1 of the 'tubular' tins either clear or black ... and place it in a very warm place before use & when not in use ... & immerse in a bucket of hot water while in use ... if it's warm it squirts ... if it gets cold it's a major pain!!
Oh and from my experience the tool that you push push push to produce a pressure squirter only squirts for under a minute per pressurisation ... so it's a LONG job to inject a whole car!!
Waxoyl Undershield ... good quality ... but not as expensive as dinitrol which has had excellent reports in the classic Car press. It contains anti-rust agents. Yes it does need regular inspection and subsequent 'touch-ups' in case it gets cracked due to flexing / or paint underneath coming away, but i have found it decent enough for the money!
NB do the welding BEFORE the waxoyling ... it is flammable!!!
(As you may expect, the above is given as the benefit of my experience and common sense + product instructions should also be used!!)