Rust proofing?

My immaculate and pampered 30k miles 'F' has been sat cossetted away under a protective cover in our well ventilated garage on SORN since late October.

Before "Madge" goes back onto the road, I am gradually going through various items on my must do jobs list one of which is giving her liberal coatings of various Bilt Hamber Dynax rust proofing and curing products, not that there are any signs of rust to attend to.

The reason for my post is to ask which of the box section members need attending to and more to the point how to inject fluid into the large and long door sill box sections on either side of the car.
In addition to the small drain holes at the rear end of these box sections are there any other places where I can easily gain access such as removable self tappers etc.?

Apart from these, I would like to remove the under wing liners so that I can the entire metal under all 4 wings a thorough clean and coating of a Dynax wax, as such does anyone know of any Youtube or similar videos that show how to easily remove these liners?

Many thanks

Not many videos but found this one to show what john explained when he did his tf.

And 1 more non English speaking vid.