Boyzone, well done you for what you said to your work mates. Good job with anti-witnessing.
I've done something similar with my extended family and some old calls. Just let them in on a couple of bits of insider information (like shunning, blood fractions, etc) and that seems to "inoculate" them against falling for the JWs. And then they tell 2 friends, and their 2 friends tell to friends and on it goes...