You have 2 methods! (Only default there is not "snap" only a % ! Better than nothing! :)
By Face (s) can be multiple in the same time! Not shown here...yes in the last images! ;)
It's like an insert face(s) with connection(s) of extremities...

By Edge ! Single!

Can works on polygonal surface of any number or edges! (Surface and edge)



Here a surface of 7 edges!

then SubD :)
You can entre more "100" but result can be unpredictable after some values! :)

I have these shortcuts (I can't memorize more)
Some sufficient for SubD Modeling in Nurbs! :)
P = Split
B = Bridge
E= Extrude
S = Scale
K = SubD

You can take a look at this thread! :)
http://moi3d.com/forum/index.php?webtag=MOI&msg=9689.1

Thank you!