As for getting underway from a quay wall or a dock... If the Current and wind are nil, push off with a boat hook. Any boat up to 50' should be easy to do so. We did this with Navy launches all the time.
Think on how you want to move away from pier side, especially if you have a bow sprite, stern overhang or exposed rudder and other delicate equipment hanging off your stern.
The name of the game is: No matter what kind of keel you have; Practice you landings and underways on flotsams, jetsams and protected pier faces. And train you significant other in doing the same. You may be incapacitated for some reason or other, and the family or friends will have to bring your boat in to the dock.
Sensible advice. I usually push off "manually" with the engine in neutral...even a 15 ton boat can be moved by a 45 kg. woman who puts her back into it. If you've got a reasonable set of fenders out, it's hard to hurt your boat or others unless you are going too fast.
I attempt most of the time to aim the boat in neutral and coast to a stop. I'm a big fan of making hard turns or "S"-turns to bleed off speed so I am coasting to a dock at less than one knot. That way, the merest two or three-second shot of reverse will stop the boat dead in the water where I want to be. I always consider, however, that the main point is not to fully stop, but to get a good spring line on in a timely fashion. When I see my wife has jumped onto the dock with spring in hand, I leave the helm and go aft to hand her the stern line and then run forward. We customarily dock with four lines, and double the bow and stern lines if we expect high winds.