When we had to supplement my son's feeds for a short time, we used to drop the bottle down a few times so that the flow would stop then we tilt it up again when he did the "let down" suck. I didn't hear about the importance of changing sides till later, but then we were only doing 1 or 2 60ml bottles a day anyway so I guess it didn't matter too much. But there is lots that can be done to help a bottle fed baby.
How can you tell what the "let down" suck is?