I need to replace the window in the cargo door of my 78 bus.
I popped the broken window out, and discovered lot of rust under
the seal.  I undertake my first rust repair on a bus...

I used my drill with a kind of grinding/sanding disc thing and a wire
brush to clean up most of the rust on the ledge, then I applied naval
jelly in hopes of getting the last little bits of rust out of the pits
in the metal.  The directions say to leave the naval jelly for 10
minutes, and a second application may be needed for heavy rust.

After several reapplications, the longest one lasting about 1-1/2
hours, and modified to include intermittant scrubbing with a
toothbrush, it looks like there is still rust in most of the places
where there was rust before.

What's the deal with this stuff?  Does it work?  Am I doing something
wrong?  Is it intended for use on only the lightest of surface rust?
Is there anything that works better?

Any advice for rust removal welcome!
Rodney