I had a partner who brought ATM up every once in a while... and I stalled on it (to date, this is the only request ever made to me that I didn't jump up and say "are you hard? Can we try it right now
?"). He didn't do a particularly winning job of selling it to me (just a mild "it would be hot"), and it seemed (seems still) not sanitary, so it would have taken a little more talking to convince me why it would be hot.
But when he arranged an MFM for me, I was enjoying myself so much that I did it without even thinking/noticing. When he told me later that he was really glad I had done it for him, I was totally shocked! I hadn't even noticed after the fact. But then he was able to explain that that's why it was hot in the first place, that I'd be too turned on to notice or be squicked out by something. So... everything went better than expected?
It really wasn't that bad---I mean, I didn't even notice! I obviously was clean before we started off on the MFM anyway.