One way could be reducing the amount of milk bottles gradually (for example 150ml instead of 180, then 130, 100ml etc) and give a solid food item before the milk. Alternatively you could also dilute the milk

Instead of dropping one I slowly increase the length between feeds as my baby started eating more solids

I paid attention to my little one when I started up solids. Maybe try giving him bigger serves of solids which should full his tummy for longer