When learning how to properly kick in Freestyle, a common mistake most novice swimmers make is that they think larger kicks will add more power to their kick. In fact, the opposite is true. If you want to generate a strong propulsive kick, you need to think smaller and faster.
I've always felt that Breaststroke was seen as the lazy cousin to the other three IM strokes within the swim community. Some believe it to be the easiest stroke and the slowest. Unfortunately, I can't argue with you on Breaststroke being the slowest. Just the natural movements of Breaststroke make it slower and less streamlined than its counterparts, but this doesn't mean that it's for the lazy or is easy to do.
Learning out to maintain that momentum is something that takes time and needs to be a formed habit. Think of it like a car, if you are driving consistently at a 100 km/h for a long period of time, then your car will use less fuel to get you there, but if you are slowing down and then speeding up, you are going to use more fuel that way. Your body is the same way during a race. If you can find a consistent rhythm and pace that works for you, you'll use less fuel meaning you have more to give at the end of a race for that potential touch out or record breaking touch.