The easiest, most economical way would be to use two rare earth magnets. We recommend 1'' x 3/4'' N50 grade which are available from several vendors online. Google search and you should find them. A smaller one will work but to achieve full saturation these are better. These are dangerous but larger magnets are very dangerous. Please use caution when working with powerful magnets.
You can make a jig using a vice. Open the jaws of the vice to full spread. Place one magnet on each jaw face so they are attractive. Slowly close the vice until you have about 1 1/2" of room. Slowly pass the pickup/magnets between them 3-4 times. The magnets will be 98% energized (saturated) immediately. (To achieve lower charges spread the jaws further apart and place a wooden insulator between them and the pickup.) There are machine magnetizers available but they aren't cheap. If you want total control over Gauss levels then a machine would be best. However you will get good results using the rare earth method.