You can have the spring line
attached to the boat or the dock. There are advantages both ways.
Attached to the boat once your line
handler is on the dock they can easily control your bow. That effectively gives them a lot more time which is what you were asking for.
I often use both.
IE fixed lines
on the dock set at the right length and a temporary line
or two attached to the boat.
Most of these suggestions apply to full length fingers, if you have short fingers and a pole 10 feet away. Your technique will be different.
It is really annoying if you drop off your line handler and they are trying to control the boat with the life-lines and either get pulled in the drink or have to let go.
Better to have a line tied to the boat so even if the wind is such they can't hold the boat by hand they can cleat
it off before you get blown down on your neighbor.
Where your dock hand gets off your boat is important also.
Rather than waiting for the stern lifeline gate they can get off midships by the shrouds which I actually think is safer as they have the the shrouds to hang onto.
The trick is to make sure they have both feet out side of the lifelines before stepping to the dock.
I actually like to have the life line gate closed until the boat is secure. That way if someone does put a hand on the life-line during docking it is tight and might do some good. Not that anyone recommends docking using the life-lines but it does happen.
BL Jones recommendation above is the defacto standard solution.
It has a lot of advantages:
If they miss you have someone on-board to help you fend off your neighbor.
If it works they don't have to get off the boat until you have powered up and forced the boat to the dock.
Some docks are configured however with rings or 2/4 cleats
so that will not work.
The problem I have with your original plan is that it implies you are planning on being all the way in the slip then prop walk the stern over to the dock. That means that the bow will swing towards the neighbors boat very fast being driven by the engine and the wind. I'm not sure you will have time to corral it before it gets away from you.
There is nothing wrong with stepping off the boat with a bow and stern line at the shrouds with the boat only half in the slip. It's easy and now you can easily control the boat from the dock.
With two people it will end up being a piece of cake. Next step is to figure out how to do it by yourself.
A couple fenders
set on your neighbors side is good insurance.