I had it done with number 1 and immediately started having contractions. Had him less than 24 hours later. That was at 39w3d.
I had it done at my appt yesterday (38 weeks exactly), felt crampy and had irregular contractions all day, then nothing. About 24 hours later, I don't think it worked. Just as an FYI, I am currently 2 cm dilated and 60% effaced, and baby is low (-1 station).
As far as how it felt, I remember the first time it being painful. Maybe because I knew more of what to expect this time, but it didn't seem as painful but still extremely uncomfortable. And I felt uncomfortable down there for the rest of the day. I also bled a lot (OB said this isn't unusual), but I don't remember that from the first time, so I just thought I would warn you because it kind of surprised me this time!