Amanda: I haven't had as much luck with w2s for naps, mostly because if I went in 5-10 mins before he usually woke, he would be dead asleep. I would pick up and shake arms, legs, with not even a stir from him. Then, two minutes later, his eyes would pop open, and he was wide awake. It doesn't hurt to be in there right when they wake, though, because at that point, I would pat/shh and it usually worked almost immediately. Or, pupd if you have to.
I'm not convinced that any direct intervention helps extend short naps, although sticking to a routine, keeping the same wake up and bedtimes helps eventually. When I did pat/shh or pupd to extend, though, once he fell back to sleep, he was able to sleep through the 40 min mark with no problem. How old is your lo? Hugo's naps seemed to get better around 4.5-5 mos, very inconsistently, but with the am nap improving first. Good luck, and you have my sympathy during this rough patch. It gets better.