If you have a manual it all depends how fast you pump if it hurts or not..if you have an electric it depends what setting you have it on..the faster the setting the stronger the suction
Manual is pointless to me. I could hand express faster then the manual.
Electric. Not painful at all.. I would hate to have a manual one .
No they don't hurt. If it hurts it would usually be due to using the incorrect size for the attachments.