I switched very early on but my milk for sure came in. If you are doing a slow transition, your body will gradually produce less. If you are quitting all at once, you will be engorged for a couple days which will result in leaking and some discomfort/pain. You can take over the counter pain meds and put an ice pack on your chest to help with the discomfort. Cabbage leaves supposedly help dry up milk supply. I walked around with cabbage leaves in my bra for a week. I think there is a medication that can help dry up milk as well but you'd have to talk to your doctor. The toughest part was the engorgement. Once you get past that, your chest will still feel a little hard but gradually soften over time. If you are gradually stopping, come up with a wean schedule. If you are quitting at once, try to not stimulate or express at all. Expressing milk tells your body it still needs to make milk.
I just went to it. I wasn’t producing milk at all