Painting inside of frame rails

Any chance at seeing a photo of this set up??

No picture, sorry.
Pretty much all my mechanical working life I have used a syphon system and blower if I needed to spray clean something with solvents and they make attachments just for that.
Instead of solvent I use POR15.
Basically something like this except mine has a hose where this one has a long metal tube.
I tape a section of coat hanger wire to the hose if I need it to reach way down inside something where the hose itself might be a problem.
Then like I said, I can vary the volume it blows in by container elevation.
Hold it up higher than the gun while spraying and you get a lot more volume of product.

You do have to drop your product back down below the gun when you let the air off, or the product runs out via gravity.
I try not to thin the product unless I have to, but Eastwood told me Lacquer thinner is fine for reducing POR15.

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