A. We have a "no soliciting" sign at the front of our neighborhood.
B. IF they do make it past that, I typically answer the door with either my AK-47 or M4 slung over my shoulder. You should see the looks on their faces. They typically just turn around and walk away (in a hurry).

Oddly enough, about 1 week ago, a younger guy in a white van tried to sell me some cleaning spray shit. I didn't have the AK with me, but my Glock was hidden in the small of my back. The spray would clean wheels, carpets, stains, etc. I knew that I didn't want to buy it, so I fucked with him for a while then told him to go on.