Tips for switching to formula

My son is 4 days old, and I was attempting to exclusively pump. I was pumping every 2 hours, and have decided to stop and switch to formula only. I need some tips! My milk just came in yesterday. Should I stop cold turkey? Slowly start spreading out my pumps and decrease how long I pump? Ice or heat? Tight fitting bra? He is adjusting very well to formula, so I am not concerned about him. Just want to make sure I don’t get clogged ducts or mastitis, as right now I am so engorged and in pain if I go longer than 3 hours without pumping.