I don't own any defense shotguns or "room brooms" at the moment but if I did, there are a # of books, videos, classes, etc available to both the armed citizen or working professional.
Classes are sometimes open to the general public from top programs or cadre.
For more details see; www.Magpul.com www.gunvideo.com www.deltapress.com www.nra.org www.paladin-press.com www.midwayusa.com www.brownells.com
Louis Awbuck(check spelling) is widely known for 12ga defense drills & training.
Author, sworn LE officer & legal use of force expert: Massad Ayoob wrote a few gun press items & manuals about shotgun methods.
DVDs are also available if classroom instruction isn't in your budget.