After seeing some pics of heavily rusted out cowls, I wan’t going to sleep last night without inspecting mine. After a peek inside with a good light, I could see some debris hiding. Removed the cover(thank GOD for this design), cleaned it out and was happy she’s still solid! Surface rust but no holes yet…I’m going to prep the area then coat it with Chassis Saver. I’ll post pics after this area is restored.
Maybe a good rust converter first then the chassis saver.
I would use something like POR 15. I just used it to spot some surface rust on my wife’s car. Just be sure to flash it with primer before it dries as it dries so hard that paint doesn’t adhere to it well.
The Chassis Saver’s designed to go right over rust. Been using it for years, highly recommend it!
Ok
I was thinking of Eastwood Chassis Black.
You’re talking about this stuff. I may give that a try on my truck.
Yes, GREAT paint! Just don’t get it on your hands or anywhere else you don’t want it 
Makes me want to go and get at my cowl now!!!
Do it, and take some pics… 
Here’s what I did to clean out my cowl:
Fortunately it wasn’t rusted through, just surface rust. I have since put POR-15 on it, but haven’t closed it up yet. I’m going to take a good look at it again before I close it and make sure everything’s covered.