They are a pain, but well worth the trouble. My "method" is to use Vise Grips sheet metal clamps. Tried to do it with fingers and never could. Put on the mag, tighten, remove, tighten a hair more and then clamp them on. All you need to do is clear the little ears that are on the sides of the mag, them you can use a punch to depress the button on the bottem and slide the base plate off. Caution is in order NOT TO CRACK THE MAG TUBE. Done about 20 this way for myself and friends with no problem.
Hope this helps.