I have had the best success with gentle pressure after the 45 min wakeup, more than any other "trick" in the book. As far as how long I keep my hands on her, it depends on which nap it is. For her first nap, I keep them on her until she's dozing off, and I can usually slip away at this point (and on the rare days, she doesn't even need this much, just a binkie re-insert). For the second nap, it takes a little longer, and for her third nap I usually have to spend 20-30 mins in there until she's REALLY soundly asleep. Then, so the change in my hands leaving doesn't wake her up, I
gradually lighten the pressure in one hand until I have it all the way off, then do the same with the other hand, then wait another 5 mins to make sure she's not going to wake up again. Sometimes she still does (her third nap is really the hardest of the day), so I start the process all over again. Usually, though, if I have the pressure there until she's pretty soundly asleep, any jolts after that don't wake her up fully. It takes a LOT of patience. And it took me some experimenting to see what really worked for her. Keep trying different things and see.
My biggest challenge is my mental boredom - I get antsy sitting there for 20 minutes not moving. I think today I'll download a book on tape for my iPod so I have something to do!
But I hear you - the "Y" time is almost non-existant for us with 45-min nappers!