The fire method is running a propane torch over the plastic. The flame never touches the plastic. It's only the heat.
Practice doing it on something else. Sun faded plastic mail box. Lawn chair. Any similar plastic as that panel. It does indeed work. The faded plastic will go shiny.
The last time I did it. I used it my mailbox and a plant pot. Plus a lawn chair. The smaller the object, the better a propane torch will work. Big objects need a bigger torch. Like what you'd use to light a BBQ pit fire.
Again, practice on something else until you get a feel for it. And if you try it. That panel will need to be removed for the best results.
I would try 303 spray first, its done wonders for me on rejuvenating old plastic.