What I did with my son, which is how the ped suggested we drop our night feeding was gradually every few days decrease the amount of the night bottle but replace it with water. Then with what we had dropped at night we replaced during a daytime feed.
If he gets fussy when you drop one time go back up for another few days. I'd say we dropped down every 3 or 4 days until the night time bottle was gone.
We did this when he was around 3 months so he wasn't on solids yet so we had to replace what we were decreasing at night during the day. I'm not sure you will have to do that since he is eating solids. But you might want to for the adjustment period.
At that time we went from 6oz in the bottle to 8oz in the bottle. We were doing 5 bottles in a 24 hour period so he went from 5 6 oz bottles to 4 8 oz bottles at the age of about 3 months. I'm pretty sure by 8 months he was only drinking like 20 - 24 oz a day with the solids.
I also (on my own) once I got down to a 1/2 and 1/2 mixture started decreasing the total volume he was getting at night. So in the end we were at only 2 oz of liquid at night and then dropped it all together after a few days.