I have a cancer inducing syndrome and have mammogram (and breast MRI) twice a year.
I am very slim with small breasts.
They will take two sets of pictures, one front and one lateral.
The technician might need to touch you and move your breast on the plate for optimal placement. In the same way a radiographer will move your ankle, leg, to get a good x-rays, they might need to touch your breast, and it is totally fine, normal and expected. So don't be surprised or shocked.
I usually only keep my skirt/trouser on and move around bare chested. It is easier, quicker than faffing around removing a top, lowering a sleeve , putting the sleeve back and so on.
You will also have to move your head/neck to one side when doing the lateral images.
For the small breasted, they have to go very close to your ribs. I was talking to a technician and she told me that with very big breast, they might need more than one imaging, if the breast is bigger than the plate, in other to have it all.
I never felt the need to take painkillers before or after.
Yes it is painful but to put it into perspective, I find having my teeth cleaned at the dentist way more painful and for a lot longer. Your breast are squished for a few seconds, but the plates will be released the second the image is done, even before the technician leaves her screen. It is painful on the moment, but the pain, at least in my case, disappears immediately.
Come back after you had it @ValerieMorghulis and tell us your experience.