I also have been thinking about header wraps. I don't want to do it first of all since there's not much room under the hood to wrap them, without taking them completely off...not worth it. Also the wrap will get filthy and will need cleaned/replaced constantly. I did hear or see that there's some silicone spray coating you can spray over the wrap to make it more durable.
The idea of spraying some coating like ceramic or something would be another idea, but I don't think it would help much. It would just get hot also after a few minutes and you'd be left with the same problem you started with.
I do have a prerunner bumper on with no mud/splash guards...one of them got ripped off and i never replaced it, so I just took the other one off. Since I have the prerunner bumper off, the stock bumper and valence is gone, so it's pretty much like running around with your pants off when speaking about keeping the engine bay cool.