Beautiful work - the glass is coming alive again for sure, especially with the reds! 
It would seem that the glass has not yet had any Triple Thick applied, as you are scraping paint away. I presume you may be going to seal it after? The reason I ask is that in some cases it would appear that sealing is the first thing to do (eg. what Nino recently did for the Buccaneer), and in other cases the sealing may need to come after.
It probably depends exactly on what is needed for the restoration of the backglass.
I generally dont Triple Thick a glass when i do this type of paint repair, since the glass has to be scraped clean. though for this one i DID give it a very light coat of TT (just over the damaged areas) before i started scraping back the old paint, my thinking was it might help save surrounding areas from losing flakes of paint as i worked on it. Some paint DID come up off the cowboy's face while i was working on it which i had to touch up
luckily it came out ok!!
Sometimes i will seal a glass im working on first with TT before i spray paint on as im doing with this BG, if there is danger of the paint bleeding under surrounding art work which may be lifting.
I'll probably give the whole glass a coat of TT when im done.
