How to slow milk supply

looking for help on how to slow my milk supply. we are almost at 1 year EPing. I want to be done at 1 year. I just started replacing one of my LOs bottles with whole milk and plan to keep replacing one more every week. I pump every 5 hours while awake and don't pump for 8 hours overnight. I normally pump about 20 minutes each session until milk doesn't come out anymore. how do I prepare for stopping. do I just stop pumping cold turkey when I'm ready or do I gradually reduce? if gradual, how? thanks!