polycrusher does get rid of polys, it had a free trial or demo if i remember right and it did a better job than the rest of them ive seen that do it for you, but like th eothers its not always the cleanest tool to use, the poly crunching programs dont do a good job at keepingthe build of the model very clean i mean, they make em sloppy as hell,
manually is the best way like they have mentioned cuz you dont screw up parts of the model you dont want to cuz you have more control over it, but doing things manually doesnt cut as many polys as the program would, (from my expereince anyways)