How Best to Clear Fender and Cowl Drains?

[1980 Big Ten]

Relatively clean, low-mileage, 1980 C10. After finding rust under the bedside molding stickers likely due to poor paint prep (see my previous posts), I am now in full rust-prevention mode. Today I got under the fenders to clear out the fender and cowl drains with an air hose. The problem is that I see no way to completely clear out the cavities between the inner and outer body panels. The 1980 version has multiple drain holes, and I seem to be able to blow most of the debris out by repeatedly blowing air into those holes, but I can never seem to get all of the debris out. My air hose can only penetrate about 1/4" into the cavities. Perhaps I should look for a long, thin air hose attachment?

My goal is to get all of the debris out before I apply Fluid Film or comparable rust prevention spray. How do I achieve my goal?

Many thanks,
D.

 

[1980 Big Ten]

This air hose attachment looks promising... https://www.amazon.com/gp/product/B07YC3ZHV7/

 

[SirRobyn0]

For the cowl drain, I'd take the wipers and cowl off. The cowling drains are huge so they'll be easy to clean out and you can blow those if you so desire. For the windshied drains I've run a wire down them to clear them out. If you use air do it carefully. If your windshield gasket and windshield channel are in good shape then it shouldn't be an issue, but if the windshield was installed using urethane, as is sometimes done when the channel is in bad shape but the owner doesn't want to pay for it to be properly repaired, or if you don't know. you could end up blowing a leak in the urethane.

 

[1980 Big Ten]

For the windshied drains I've run a wire down them to clear them out. If you use air do it carefully.

Many thanks. I’ve seen the windshield drains in photos but not yet on my truck. Will spend time on those—carefully.