Not sure if you had acess to a blaster. That would be the best way but it takes a while.
Rick, those are rust removers and not to be confused with converters or sealers. I left a rusty bracket in this stuff over night and it came out looking like an NOS piece after wards.
There's a few videos of the stuff being used. One where a guy it treating a hood section. He made a dam with tape and plastic and let it soak. A perfect technieque for a roof panel.
A vid of it used on a coil spring.