Quoted from Arcane:
I would try to clean up and restore the old lift-up channel attached to the backglass. You may damage the rear of the backglass in the process of separation, especially if it is already flaking.
Restore the old lift channel while it's attached to the backglass?
The original lift channels were stamped from cold-rolled sheet metal and had cheap nickel plating. Once they rust that's it unless you were to remove it and possible re-polish and re-plate it.
I make reproductions out of pre-polished stainless steel that will never rust.
It's best to remove the old one even if you lose some paint from the backglass. Afterwards you can touch the backglass up and then I mask off about an inch up (or however high up I need to go to cover the damaged area) and spray a stripe of Triple-Thick over the touch up. After you install the new lift channel it is usually hard to see and the repair is permanent. The lift channel usually hides the areas that might be damaged and the area that fits in the lift channel groove is reinforced.
Always use the tape when installing a lift channel. It keeps the glass from cracking and acts like a shock absorber cushioning the glass. Never put a bare metal lift channel on the glass unless you don't care if it's ruined.
The groove in the lift channel is larger than the glass thickness to allow for the use of tape.
Here's what a typical original lift channel looks like. They rusted-out because when the glass is cleaned the Windex or whatever was used just lays in the groove. It's also a contributing factor as to why the bottom area tends to flake before the top does.
Here's one of my new lift channels next to the crappy original:
Afterwards the backglass and trim are like new:
I also make the plastic edge trim:
I have several machines with touched-up bottom areas and a stripe of Triple-Thick across the bottom. It stops the paint separation in it's tracks and preserves the backglass from further damage.