Ruat proofing confusion

[MarcT4]

Needing some advice - what's the best way to protect the underside of my T4?

It's a camper. 1997. It's in very good nick for the age.

Right now the factory underseal is starting to come off and have small rust spots. Nothing major but want to get on top of it.

There's a lot of differing information about this online. A lot of snake oil salesmen too...

Is the best thing to do to get it up on axle stands, remove the failing protection with some poly disks/angle grinder, clean the metal, then use an epoxy primer on the chassis and underside (or use epoxy-mastic one coat paint)?

That seems like the most long term fix?

I know there are solutions like waxoyl and dinitrol, but is painting a better solution?

Or at least, do the above to the visible subframe and chassis, then spray a waxoyl spray on top to cover any gaps?

I don't have air compressor or spray gun, so will be painting on by hand. Or the aerosol waxoyls.

[G600]

Have a look at bilt hamber products, they do everything you need and it's the best stuff I've used.