I do not bake the dirt or use a magnate as I had already did much of my layout before I read about any one doing these things.
One other thing I have used that is not mentioned is to use a coffee bean grinder for getting the soil very fine or getting different colors mixed together to darken or lighten the color. I also use the grinder to get ballast finer or the add some dark dirt to change the color of it.
I have also use Prayer59's method to apply the soil as well as others I have developed for certain looks.