@Ganderoleg :

So: After retopology in 3D Coat models preserve their connections with bones?
But why does it looks bad? What does retopology do? Blender's poly reduction script only cut's down vertex number trying to preserve model shape, nothing else.
I guess retopology process (in 3D Coat) finds nearest vertex to the place you draw squares and cut off all other vertex?

In fact polygon reduction and retopology are two different tools.

- Polygon reduction tool :
Reduces polygons automatically for yourself.
The problem it deletes vertices that would be better to keep to have a good disposition of polygons (fro animation for example).
It's only delete nearest vertices, so results are not as good as if you modeled the low mesh yourself by hand.


- Retopology tools :
You create the low poly model, not an automatic tool, but retopo tools allow to you to work on the base high res mesh.
So that's very easy like in the video.
Just draw lines over the high res mesh or draw quads !
This way , you produce lot more better result than an automatic tool in terms of polygons reduction and the way they are disposed !


3D Coat don't know anything about rigging in fact.
You can just export the low model with normal,diff and spec , maps.

An example :
Reduction tools , won't make such good low poly model edges and faces flow :

With retopo that's to you that' decide what faces to create, and retopo bring very fast way to create low poly mesh !