We don't think to many will debate the stopping power of a 12 Gauge shot gun for self defense. Just the thought of the consequences or the sound of the action is typically enough to get the job done. However, this does not stop the question as to how to take the ammunition utilized and bring it to its fullest potential and at a cost savings.
We don't fully vouch for making your own wax slugs as we have not done this ourselves, nor do we know if you will end up blowing up your own shotgun or worse. These guys did just that by doubling up loads, which even they don't recommend, but the results with a standard load are quite impressive as shown in this video. They do have other coverage showing how to make the wax slugs which you can do at your own leisure.