Rusting wheels

 I work as a mechanic. I use a product called PB Blaster. Should be available at an auto parts store. Asumming you don't wan to to disassemble the cars trucks. I would spray the product in a container. And then pour it into a small needlepoint dispenser. Apply it where the axle goes into the side frame. Let it soak a bit and reapply. Often times a project that I won't get to the next day and I know I'll be dealing with rusty frozen bolts. I spray the Blaster on it every now and then. Usually the next day it will loosen up. The key is to let it work. After it has sat a while. If the wheels move somewhat freely. Then hit the wheels with a Dremel with a soft wire brush while it's upside down in a cradle. You'll be surprised how fast they will spin if they are free. When you remove the Dremel they still should be spinning. When your satisfied re lube them with a good lube such as Excelle from JT's (a forum sponsor) or Labelle.

I know PB Blaster well, it has loosened many a stuck bolt and nut on my 84 GTI.  I can't believe I hadn't thought of that!  Thanks you!

Sand it lightly. It's how I returned my great uncles 2243 F3 combo back to service

I do not know this for sure, but I would be careful with PBblaster around any plastic parts and paint.  the old demo from the auto-parts store leaves me a little worried about contact with non-metal.  the demo showed the pb blast melting styrofoam cups where wd-40 did nothing.  

as a side, do NOT use wd-40, as it will harden over time causing you lots of problems.  

I've melted plenty of styrofoam cups with Blaster.  lol    WD-40 is definitely off the table.

I think I should disassemble the trucks to clean them well, but I am not sure where to start.  

I would pull the axles and wheels out and clean them with nothing more than 3 in 1 machine oil. Use the good brand name blue shop paper towels to avoid lint. The machine oil will clean the rust off and prevent future rust without making a mess.

Uh, oil?