i put standard insulation set on my bonnet, and thats had not effect on operating temp with my engine.
looks good, 10 points for effort mate.
the high temp spray, i used that on some calipers, its got a matt finish and i didnt like it tbh. so i left it to cure and then laqured it a few times... did the trick though. total waste of time using high temp paint in the end though.
just hammerite the rocker, or even better, get it polished!