You do this by improving body balance, position, and alignment. Clean up your body position, and even if you don't make any changes in your stroke, your still imperfect stroke will move you further and faster. The second way is creating more propulsion by locating your power source and using your hands more effectively. So get to work on the eliminating skills first because they offer more opportunity for improvement. Make your body longer.
Longer boats go faster.
The same goes for your body. That keeps your body longer while your other hand completes its stroke and takes over the front position. In breaststroke, after pulling, stretch and streamline both arms forward and keep them there until after you complete your kick. Longer body, faster body. Improve your hull design.