Clarification
The brush AC electric motor consists of very few parts. The armature, two bearings on either side, a field coil, brush set, and a motor housing. The field coil is the large metal block that looks like 50 thin metal plates fused together with magnet wire coils on either side. In your case it is also part of the housing. It can have two or four wires attached to it, one leading to the brushes and the other to line in the two wire configuration. I forgot the four wire configuration. The armature, which would be the large circular object that spins and also has magnet wire windings has a section at the top known as the commutator. The commutator can be characterized as around 20 copper plates in a circular arrangement near the top of the armature. The carbon brushes, which are two longer usually rectangular in nature graphite blocks make contact with the commutator providing the armature windings with power. below the armature windings the grounded shaft ends can be found. those ends have bearings attached to make the shaft spin with reduced friction. The lower shaft is always longer due to the fact that that is were the pulley or fan are mounted. In most cases there is a cooling fan on the top of the lower shaft. It is usually jammed to remove the main pulley or fan. The main pulley or fan is usually reverse threaded onto the shaft. Motor bearings in your case are the two large pieces attached to the field coil. There are two variations of bearings. Ball bearings require high temperature grease to be properly lubricated. Sleeve bearings, usually bronze, require the blue and white 3 in 1 oil. Your bearings sound corroded to the armature shaft. There are also sleeve bearings on the brush roll which also need to be freed and oiled. Since you stated that your shaft is seized with the bearings, you will need to break down the corrosion binding it. The brusheoll bearings must be treated in a similar manner. Try some liquid wrench oil for freeing up the bearings. When I say break cleaner, I mean the stuff they sell at auto zone that gets oil off stuff. It gets off the old burnt up oil and grease. It must be used to clean the bearings after they are freed. And yes, a wire brush can be used as a substitute for the wire wheel. The wire wheel is just cleaner and more thorough.