Technology has improved quite a bit in the modern era for charging and testing of aircraft magneto magnets. The gauss meters are more precise than the old needle movement magnetometer measuring devices. Most aircraft magnetos have a rotating magnet so they don't compare the same to the old Model T mageto V-magnets.
Most of my magnetizing and demagnetizing experience was with magnetic particle inspection equipment of the procedure known as Magna-Flux. The best magnetization is done by having the coils actually wrapped around the two poles of the magnet. The old model T stuff just butts the magnet poles up against the edge of the coils. It gives a sufficient gauss but the modern methods would give a higher magnetic gauss that would likely last longer.
An old International Harvester magnet charger that I found on the internet was set up so the magnets that were horse shoe shaped would fit into the coils for charging but I don't think that would work well for the V-shaped magnets.
This linked thread from MTFCA is pretty interesting about how one of the responders charged his V-magnets.
http://www.mtfca.com/discus/messages...tml?1358959226
The key is getting all of them about the same in strength of gauss.