Classic car restoration magazines run articles about repairing worse rocker panel rust than that. Usually the restorer cuts most of old stuff completely out, then uses pattern replacement parts, not just sheet metal. “Pattern parts” have the right shape, but have to be cut to size as I understand it. Seems a lot simpler than trying to fabricate a replacement part using sheet metal. For some reason they usually seem to use a MIG welder with an inert gas feed. Maybe theyjust don’t have a TIG unit. MIG flux welding is seldom used in the articles. I think the reason is b/c those types of welds require a lot of after-weld cleaning and surfacing before you can apply paint. After MIG/inert gas, the next most common method seems to by oxy-acetylene torch welding.
On a regular wire feed you are usually using .030 sized wire flux core. This is too big for sheet metal usually although I have done it on thicker sheet metal. If you add the gas, you go with .023 or .024 wire solid wire with the gas shielding the weld. This takes less heat to burn through the sheet metal and reduces the chance of warping the panel. Yeah sure you’ll see YouTube’s on guys using solid core on body work, but most ( i have no statistics, just folks I’ve talked to) body people will use gas and the small wire for patch panels. I’ve had a gas tank for over a year and think it is a lifetime supply.
The OP has already lanolin coated the rusty bits under the car. Lanolin is a rustproofer for parts not already rusted. It will do little to prevent further rust.
Lanolin will prevent further rust, thats its purpose. Put it on already rusted parts and it will prevent it from continuing to rust. It displaces water too so any moisture on the rust will be displaced, compared to say a rust shield spray paint which traps the moisture under it. Rust requires water and oxygen, lanolin like a layer of grease prevents both from contacting the metal and rusting stops.
The rust is already there waiting to fall off and expose the bare metal under it. Lanolin treatments and virtually every other rustproofing products are for coating surfaces not yet rusted. They are a stop gap at best on new cars. On rusty ones, they are of little value. Especially since you can’t get it INside those areas that haven’t yet rusted through.
The only products I have seen for rusty surfaces are rust convertors or encapsulators.
I have been fighting rusty cars for almost 50 years. Rust never sleeps. Anything short of dunking the entire body into an acid strip tank and replacing the holes left after dip slows it only slightly.
Nope, only way to stop rust is to remove it.