If you now or previously owned one how long did it take you to learn to

maneuver it properly at low speeds, most especially in reverse and in
wind?

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You never stop learning.

Each situation is different, and not all are possible to specifically
rehearse in advance.

One needs to put the boat into the slip *mentally* and develop a game
plan (taking wind, current, and known characteristics of an individual
boat into account) before ever getting into a tight spot.

The most important consideration, IMO, is understanding how the boat
will walk in reverse.
Depending on LH or RH prop, the boat will back to port or starboard.
Proper boat handling acknowledges, rather than ignores, this "ism" and
uses the phenomenon to control the stern when docking as well as when
reversing in general.

It would be interesting to understand what you define as "walking" a
single screw to the dock.
If you mean moving the bow and stern simultaneously to approach the
dock beam-to
from several feet away that's a manuever not usually accomplished
without a thruster. The more common practice is to place the bow near
where it needs to go and then bring the stern around the pivot point to
the dock. One needs to allow for some forward movement of the bow when
pivoting, but it is no trick at all to put a 36' single screw into 40
or so feet of float space with vessels moored fore and aft- with some
practice.

One excellent concept to appreciate is that you want to dock to the
outside, rather than the inside of a circle. That can make a huge
difference. You see guys turn into a slip from the "wrong" direction
all the time, where they are being forced against a neighboring boat
rather than against the float. It's often better to pick a slip that
allows you to make an outside turn, or proceed down the fairway, do a
U-turn, and come back (that will change the dynamics of the docking
circle).. I have found this is important with any boat, but more
particularly with a single screw than some other configurations.

Steering in reverse is a challenge. Some boats do better than others.
Mine does rather well, but backing up over a great distance and with
any accuracy means paying constant attention to the effects of prop and
rudder. Example: My boat backs to starboard. To back up in a straight
line, I turn the wheel to port. At very low rpm, the boat tends to
follow its big rudder rather than the prop walk, and the boat will back
to port. With a little more engine speed, the rudder and the prop walk
eventually achieve a sort of "balance" and the boat will back
relatively straight. At a higher engine speed, the prop walk overwhelms
the rudder and the boat backs to starboard. Even so, there's no shame
in using a bit of forward thrust to "straighten out"
partway through a long backing, particularl in a ross wind or current.