the guys going into a slip with momentum and then reversing to avoid a crash will sooner or later run into the slip and with momentum it will make more than dents.
Depends on how what you consider momentum.** It's all a matter of judgement. You need to keep way on to mainain rudder authority, but you want to be almost stopped when you reach the point where you're next to your finger as far into the slip as you want to go.* It takes a good feel for the decelereation rate of your boat plus knowing how the particular*current or wind or both that you have to deal with affects your steerage and deceleration.
We turn toward our slip at idle speed (a bit over 3 knots) at which point we have great rudder authority.* But we know the deceleration rate of our boat when we shift to neutral so it's all a matter of judgement and timing to bring the boat alongside the finger all the way into the slip just as the boat comes to a stop.* And we use differential thrust or offset thrust to move the stern or, do a degree, the bow as we slide in to put the boat against the finger.
It's one of those things you can't describe in words, you just have to do it and learn the sight picture and the characteristics of your boat.
In many ways it's exactly like docking a floatplane although the boat is much easier because you have big water rudders, reverse, and*in our case differential thrust.* In the floatplane it's ALL judgement because you shut the engine down some distance from the dock and let your momentum carry you in.* And because floatplanes are so easy to damage you have to arrive at the dock just as the plane is driting to a stop.* Not so hard in calm conditions, but it can get tricky with a contrary wind or current or if there is only a small space at the dock between planes.* I find docking the boat is the same only I have a few more aids at my disposal.