LOL Lou!
Actually I have been QUITE lucky in that regards! For most of my immediate family I just asked. I was worried the most about my father-- stressed over it for weeks even after purchasing the test. Finally I worked up the nerve and was shocked when he said yes without any questions! All that stressing (and weeks wasted) for nothing. I've even had surprising luck when asking relatives that I've just met. I don't what it is--I usually start talking about my research and things I've found about the family and just kind of work it into the conversation. So far so good-- I'm 19 for 19. ;)
ETA: I DID have a devil of a time getting my granddad's 1st cousin once removed to test. He agreed and I sent him the kit and then he wouldn't do it. I kept reminding him and he kept ignoring me so I finally gave up. About a month later he told me he had just sent it in. I was very excited because I would FINALLY have someone to compare my dad's paternal matches to. Turns out they did not have any dna in common--which should NOT have happened. I haven't figured out yet where the "disconnect" is. But I wonder if the cousin somehow suspected how the results would turn out.