I agree it probably works better in blindfold play, but it works well in normal simul too (I used it successfully once, though that wasn't against a GM, and I had fairly recently stopped playing competitive chess).
Now going way off topic, but Krabbe's cycling book "The Rider"[1] is probably the best book about cycling I've ever read. Along with "Once a Runner"[2] I think it probably the best piece of sporting fiction ever:
My whole life had only one goal: making that last wheel, here, now. I was wasted. But that elusive finish line, eight, seven, six and a half meters in front of me, kept my hope and desire awake. I coughed and slobbered. I remembered the words of advice ‘Shift, when you’re really, truly at the end of your rope, to a higher gear.’ I shifted. A few hysterical kicks on the thirteen, then clenched power of a mortal struggle. I was there. I was sitting on that last wheel. I was in the lead group.
[1] http://cyclingtips.com.au/2010/11/the-rider/
[2] http://www.slate.com/articles/arts/culturebox/2008/12/speed_...
Anyway, this reminds me of an anecdote I read long ago in a Tim Krabbe piece:
"A grandmaster once played a 10-board blind simul somewhere. Knowing the ropes of blind simuls, he varied his games right from the start, maybe opening two with 1.e4, two with 1.d4, one with 1.b3, and so on. To his suprise, all of his opponents played 1...b6. On the second move, five of them played 2...Bb7, and the other five 2...Ba6. On the third, three of the five players who had played 2...Bb7 now played 3...Bc8 and the other two played 3...Ba6, while three of the five who had played 2...Ba6 now played 3...Bb7, and the other two 3...Bc8. On move 4, the grandmaster saw bishops everywhere. After move 5, he excused himself and went to the toilet where he was happy to find a window big enough to let him through."