I take very opportunity to chat with them about three key issues:
1914
Overlapping generations
1975 and the other failed prophecies
And now the new one: the GB aren't god's chosen, according to GJ. This particular one (video of him using "presumptuous") is on my phone as are a few others.
A few different scriptures so they don't assume I'm someone who's clueless about the bible.
I NEVER talk atheism with them, I find it instantly shuts them off. For me I've always had better success picking topics they can immediately identify with or better - have experienced themselves, like the 1914 gen almost all being dead but still no sight of the end.
If I seem them offerimg someone literature or having a chat I ALWAYS interject and ruin their "pitch".
Since I gave the last two who came to my door a good talking to, I haven't seen one in my neighborhood for at least a year.