Chemetall "Blackguard" for inner panels.

[Rufus]

I just coated the inner panels of my sandman with "Blackguard" rust convertor.
The s*** is good stuff.
A light sand to remove any loose rust then apply straight on with brush or spray.
Seals and converts rust with a glossy black-ish finish.
I would recommend this stuff for inner guards and underbody application.

Touch dry in 30mins. 1-2 coats is fine.
Can paint straight over it.

More specs available if interested.