Breastfeeding/pumping questions?

Hi, I’m looking for advice for pumping mainly. I had my second baby a few days ago and they were born early and went to the NICU right away. I didn’t breastfeed my oldest and with everything going on this time I decided to bottle feed at the beginning. Now it’s a few days after the birth and my boobs are hard as rocks and I feel like my milk is finally coming in. I’m not really interested in breastfeeding but I’d like to try pumping to see if I can express some so that baby can get some of the good antibodies. Did anyone exclusively pump or start after a couple days? Can it still work? Any advice would be helpful 😊