Breastfeed to Formula

Hi, exclusively breastfed po si baby up until 6 mos but recently, inuunti-unti ko na po siya sa formula milk kasi by june 10 I will be going back to office work. Question ko lang, how do you guys handle breast engorgement or weaning lalo na in a short period of time? Also ilang days po kaya bago tuluyang mawala yung milk ko or at least di na masakit sa dibdib na yung mabigat pakiramdam? Ty!