There are several things to keep in mind when using the magnetic primer. The first thing is that the pigments in this particular product are quite heavy and can settle to the bottom of the can. Thoroughly stirring before use to get all of the pigment re-incorporated into the paint is essential.
Also, it's important to use the right amount of paint for the area you're painting. Ideally, one quart of the primer is needed for about a 16 sq. ft. (1.4 sq. m.) area. If the product is not applied heavily enough, you won't get the full magnetic effect. If it takes more than 3 coats to get the proper amount on the surface, that's ok; simply keep applying until you have the correct amount on the surface for the area that you are covering.
The smoother you get the primer on the better it works, since the magnet will have more contact points to hang on with, so a foam roller is recommended for application. Larger, flexible magnets are usually the best to use, since they're stronger and have more surface area. As a primer, this product can be painted over with just about any kind of wall paint without affecting the magnetism.