Thanks for the tips! It works great with translation as well. I have been looking for a long time for a way to snap with axis constraint and that's the way to do it. Not the most intuitive thing but once you know it it's great.
Great tricks ! I didn't know the extended axis tool...I found yet another way : activate the guid line snap, and then you can align the polygons without the 180° flip ! Great stuff anyway, please continue ! ;)
This technique would be more correct by starting with a workplane aligned to the one polygon with which you trying to align the others. Then you can use all of the same techniques to align the other polygons, starting with the polygons around the one you are aligning to and working your way out (in a "grow selection" type of manner).
You must tell the viewers : this method is not suitable for the large model that has many polygons and edges, and it is necessary to use the Axis Center tool first, then the Axis Edge alignment tool.