I may be wrong, but I think the only way you can undo a smooth is if you haven't deleted the history on that object. If you haven't deleted the history then look in the input section of your channel box and there should be a smoothFace somewhere in the list. If so, click on it to expand and find the divisions option. Change it to 0 and it should undo your smooth.

Instead of using smoothing, try converting your polys to subd's. You can go back and forth between subd's and polys until you get all your tweaking done. Once you are satisfied then do the smooth.

Hope this helps