Fiberglass Insulation under hood. How to clean?

[pixelmonkey]

In some vehicles, a molded piece of fiberglass insulation is used under the hood.

I've always just used some APC and a soft scrub brush to clean any road salts, dirt or oils from them, but i'm wanting to know if anyone has a better suggestion or method to clean the insulation.

chris<pixelmonkey>

 

[Wors]

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[pixelmonkey]

bumping this one up for other members to offer suggestions.
chris<pixelmonkey>

 

[POPPAJ]

On newer vehicles that have the semi-hard insulation, I use armor all spray tire foam. Spray it on a small area, spread it around with a soft, long bristled tire or wheel brush, move on to the next area. Sounds kind of crazy, but it works well. You can always experiment on the wife's car!