Internal cavity rust treatment, Would/do you use Ospho? Options

[bbrock]

This question is specifically for those enclosed cavities that do not get opened during a full rustoration. On my car, there aren't many (inner cavities of roof pillars, roll bar, windshield frame, trunk cross member, and inside driver's suspension console). I bought a bunch of tubing to modify a garden pump sprayer so I could spray Ospho/Jasco inside those cavities. My thinking is that it would seep into seams where there is ALWAYS rust even in parts in good condition, and convert whatever rust it contacts. This would be followed by treating with Eastwood Internal Frame Coating, and finally, 3M Cavity Wax Plus. So two questions about the Ospho treatment:

1. Would you do it? It makes sense in my head, but it is spraying acid inside structural components.

2. If you did, would you follow with a water spray to neutralize the acid? My understanding is that the product forms a protective coating that can be left indefinitely, but it needs to be neutralized before it can be painted. For internals, I wonder if I'd get better long-term protection by just spraying Ospho and leaving it alone.

Thoughts?