the triangulating all the the mesh then exporting then i experienced the error you are having when the meshes weren't exactly the same and dont use the substance normal export
The tutorial PhattyEwok posted is pretty awesome. Definitely sent me in the right direction. Using that, trial and error, and close observation of random objects should help.
The odd noise seems way overkill depending on the shot. It almost works well in the second but makes it look like you've got a rendering error in the first.