Best tool yet, for me..
Single edge razor blade.
It'll cut off all the active rust.
Then steel wool n WD-40.
If that doesn't do it, out comes the wet n dry paper @ no more than 600 grt. to start, and adjust my grt. as needed.

Always the least evasive first.
Its hard to beat the SE blade for rust removal.

For the jimps I've used a stainless steel tooth brush, or a bore brush from a gun cleaning kit. For the worst in the jimps I've resorted to the dremmel and a SS wire wheel ( last resort). But still hard to beat the SE blade. [emoji6]