Welcome to the Forum !
The clear coat is going to continue to die off because the entire panel paint is dead.. Nothing you mentioned is going to help it for very long.
The normal way to remedy this is to completely strip ALL the paint off, clean really well, prime, repaint.. Yes, I know, this is not your intention or in your budget..
Yes, you can do whatever you want, but it will never look "normal"..
If you are ok with that then please be careful and as has been already said, use an OSHA rated respirator, so you don`t inhale those fumes..
I read that clear coat link from 2011...
The question about "back taping"... Painters do this to help Not get a definite "Line" where the paint ends, and then you have to now sand that line down level, to the rest of the existing paintwork..
Sanding - Do as much as you can, using a "Block".. They make the traditional thick, rubber, hard one that holds a part of sheet of sandpaper and thinner ones that have some flex to them... I have used the thick rubber hard ones very successfully for decades and never had an issue...
You Want to have ALL the area sanded flat, so there are no lines, indentions, etc.., showing..
How do you know the surface/s are flat???
You get a can of black lacquer thinner at the paint store, shake it up, and carefully, spray a LIGHT mist over the area to be sanded. It`s Called a Guide Coat..
Then, when you Block wet sand this down, you have a Visual of where you sanded..
You can see any High or Low Spots in the work, as you go and address them Before you put the color, clear, down...
For example, in that old link from 2011, if the guy had sprayed that Guide Coat on his work after he sprayed it, and sanded it with a Block, he would have immediately seen the Guide Coat completely Gone from that high spot line..
And when he eventually sanded it down to the Level of the rest of the work, and the Guide Coat started coming off the rest of the work, then that panel would be flat...
You also need to use your hands to feel it, after the surface is clean, dry and your hands are clean and dry...
Tape and paper off a Lot More than that video... Paint tends to go everywhere and you don`t want more work, taking it all off later...
I have seen zillions of vehicles that were supposedly painted by a pro and the Glass has some paint on it, because they did not tape off the glass
Back Tape= Get a paper and tape machine, they even make a hand held one at Home Depot, or they used to...
Load your masking tape roll and paper roll on it, and get the masking tape started on the paper, so when you pull the paper out, the tape comes with it, all stuck to the edge of the paper...
Take that paper and masking tape you cut off the tape machine, turn it upside down so the masking tape is at the bottom and the paper it is stuck to is at the top..
Tape the panel wherever you are going to tape it, with the paper still at the "top", and when done getting the tape stuck, carefully "roll" that tape and paper edge "Over", in front of you, so that the tape is also "rolled" a little with the paper, and attach that paper edge somewhere down, to the side, of where you started the tape...
Do not pull this back tape too hard or you will flatten out the tape and paper, and you don`t want to do that.. You want that tape and paper edge to be more "Rounded"....
When you now spray "in" that area that is all Back Taped around it, you will concentrate on the target area and whatever overspray you make will get mostly held up by that rolled edge of tape and paper, so when finished, there will be No Line of material to deal with later...
Good luck with this !
Dan F
