The problem is that you'd have to descend rather steeply for any sort of "braking" to work. In practice, you're unlikely to get more range by descending steeply

The problem is that you'd have to descend rather steeply for any sort of "braking" to work. In practice, you're unlikely to get more range by descending steeply and then using the power gained from that to fly level than you would get by descending at best glide angle.