I have cleaned and restored a fair amount of old machines and a few hand tools. It's really not that hard, just intimidating. I totally agree with the wire brush comments. I use steel but brass will work too. If you want brass look close at the label. Many are steel wires with a brass finish on them.

If you can find them another good tool if the rust is not really heavy is scotch-brite disk on a grinder, might work on a drill? I found some recently at the surplus store and mounted them on an old motor and there great for cleaning metal, but not for heavy rust.

It is more involved but still pretty simple, for the hand planes electrolysis is a good option because of the nook and crannies. Search for 'electrolysis rust removal' and you will find several web pages on how to do it. Some people go over the top and make it hard but it's really easy with a battery charger and some old steel scraps. I have done it on a small and big scale. I once made a tank out of concrete blocks and vinyl sheeting on my car trailer to clean a large base of a saw I bought. Used a 55 gallon barrel of the tables off my 12" jointer. When there is a lot of nooks and crannies this is what i use. I love it because I can set it up and just leave it for days if I want.

The only down side is it will remove any Japanning on the plane, if there is any left of course. It is also a good way to remove old paint. It will cause it loosen up and just scrap right off. Not sure why but it works!

Jeff