I didnt use bbq paint but i used high temperature engine paint made by krylon for something like 1200 degrees or some nonsense.
I actually sprayed most of the metal parts of my bike with it including the swing arm, rear sets and passenger pegs, clutch cover, alternator cover, and a large portion of my engine block up to the cooling fins on the left side.
It holds up really well although it was not as black as i wanted it to be and i dont think they make it any blacker. But it hasnt melted, faded, chipped, cracked, bubbled, or anything like that except for a part of the alternator cover which i went over a second time with a non high temp paint, which was only a mediocurly bad idea.
IMHO i think its perfectly fine and safe to use it if your looking for a cheap powder coat alternative and are willing to prep the areas and tape off properly, but if you can save the cash and get it done professionally because it looks killer and you know its done right.