I don't have much pumping experience. I have a double electric pump that I used for a while. I stopped pumping because I couldn't get Kyah to take a bottle for nothing in the world! I have never tried using a manual pump. I would assume that it pretty much works the same just one is manual and the other electric. I really don't think it should hurt. It didn't hurt when I pumped. I know my electric pump has several suction settings that range from soft to much harder. Maybe your pump just has too much suction power? Are you making sure your nipple/areola are centered into the pump correctly? I was thinking maybe it was off a bit? Maybe try placing a warm damp towel around/on your breast to help relax?
Hmm. I wish I could be of more help! I bet some of the other Mommies will have some great advice