Take a spring from bow to shore. Put lots of fenders up
front. Apply full helm towards the shore. Slowly add power.
The stern will walk away from the shore until you can back
off from the quay in comfort.

Of course, but what does that have to do with an observation that with the helm
amidships you won't achieve enough side thrust from the prop to kick the stern
away from the dock?

In a *moderate* wind, the spring line is usually unneccessary. Removing from
the question originally posed to the board any variable that says the rudder
cannot be used allows the rudder to be turned toward the dock, and a brief
application of forward will indeed "kick out" the stern. (Just have to make
sure that you don't whack the stem in the process)