The Watchtower's own words are what convicts them. At the time my wife and I decided to start our research, knowing it would probably lead us out of the organization, we had no outside information at all. (This was well before the internet). All we knew was that what we were hearing from the organization did not match reality.
I think a gentle "Hey, look at this, I found a video of a GB member let's watch it" sort of invitation will not raise the shields into anti-apostate mode. Then you can make some "gee, I didn't think that's what they've said in the past" comments and go look up (as suggested above) previous comments about soliciting funds.
It might add up to a real eye-opener.