Firstly, it's fine.
Last Thursday my midwife tried to have a go but couldnt because my cervix was posterior (behind baby's head) so she couldnt get at it. However, ended up going into triage on Saturday afternoon (dont ask!) and the hospital midwife had a go there. She said she didnt know what thursdays midwife was doing, but she found it 'easy'.
I wouldnt compare it to a smear test as I find smear tests painful -the speculum hurts me and I come out in a sweat. Proper HATE smears.
Sweep does NOT involve speculum OR horrible scraping sensation that you get with a smear test. Essentially, the midwife inserts 2 fingers (sorry if tmi, but you did ask and makes a circular motion around your cervix to try and separate the membranes. Its 'uncomfortable' (and slightly undignified) but not painful. It made me 'make a face' but thats it -the expectation of what is about to happen is far worse than the actual event.
Midwife said it might trigger some period type pain and spotting. I had the period pain & baby became VERY busy that night, but no blood and nothing else happened. However, last night I had the characteristic 'show' (that basically looks like youve had a cold and blown your nose!) so I now know that it was successful.
Hope my explanation helps. Good luck!