Manual dynamic range reduction

I played a little with HDR software but wasn't always happy with the results. Often it would look better to just combine exposures (if done, otherwise just one RAW image) and use masks derived from the images. So I tried to play with an older image that had a correctly exposed sky, but several stops underexposed foreground (it was dawn inside a canyon). I simply used a mask generated from one of the color channels with a exposure adjustment layer in PS. Came out quite well I think: