I recently got an Arisaka bayonet with a beautiful blade but rather rusty elsewhere, especially on the scabbard and pommel.
I cleaned it with a technique I've used dozens of time to remove active rust without harming the underlying surface.
I liken it to wet sanding during varnishing, using a nylon pad and WD-40 to keep everything soaking wet. I also use brass brushes including rotory brushes in a Dremel-stype tool. This is not a process that shines your blade: It's very low impact and I've found that the nylon and brass only removes the loose rust. Never once has anything happened where I said "Oops!" .
But - as happened with the bayonet shown in this video - I have often found surprises hidden behind the rust.