snip
Heavier deposits of rust and thick dirt, grease etc. will all come off
quite easily if you soak the tool in petrol for anywhere from 1 hour to
overnight (I think diesel is even better but I won't swear to that because
I haven't tried it). Scrub with a wire brush, repeat as needed and then
proceed as above. I would expect that "medium" deposits of rust can be
removed using wd-40 or CRC or whatever you have.
snip
You can remove all traces of rust by soaking the metal in molasses.
Sounds strange, but it works really well. Buy a small tub of molasses
from a farm supply shop, mix with water at about 10 parts water to 1
part molasses.
Stick the rusty implements in the mix and leave to soak for however
long it takes.
Small rust marks will disappear in a day, heavy rust can take about a
week.
If it takes a week, the mix will get a covering of a marshmallow sort
of mould. It's harmless as far as I know, and doesn't smell or
anything.

My Dad heard about this from a guy restoring vintage cars - it's light
on elbow grease and doesn't abrade the metal. I've since used it to
great effect to restore some old tools - files, screwdrivers and a
saw.
Once they are done, oil the metal so no more rust forms. WD-40, CRC,
RP7 are all fine for this.

Good Luck !

Adam