Grinding was pretty tough in those tight areas and I couldn't fit my hands in to sand. Part of the reason for the paint was after a wire brush, that's about all I could get off. There was a fair bit of junk pulled off the surfaces. I'm hoping the rust converter handles what I couldn't reach better than just leaving it all there.
Is this what I'm looking for and is it applied after welding, or between the seams before welding?
https://www.amazon.com/KBS-Coatings-...=3m+cavity+wax
Looks like this may be easier than I thought to apply
https://www.youtube.com/watch?v=m2cUlmfW9a8