The first thing I would do before dissemble a vintage machine, after unloading it into my shop, is to print out a machine manual and a part list with the drawings of the machine. The machine manual and part list can be found at http://vintagemachinery.org.
I would dissemble the machine and compare it against the drawings. This will help me identify any missing parts and also help me understand how the parts are assembled together. I also would label every part that is taken off from the machine and store them into a plastic bag. In addition, I took pictures during dissembling.
For nuts/bolts that are hard to turn, I use WD 40 or Blaster Penetrating Catalyst. To lubricate, I use machine lub oil for general lubrication. On my jointer, the threads on the machine lead screw are smashed. I used dies to clean the threads.
Below are a picture of the dissembled jointer and a picture after restoration (I am too lazy to re-paint it, BTW):