Sorry for not being clear. There are a few ways to rig the lines. You can have a buoy on the end so that they are floating but this risks getting wrapped around a tire or in your prop. You could also lead the lines forward to the winch platform so you could come in and get the bow hooked up then figure out the stern placement. I am sure that it is one of those things that you would figure out an improved method specific to your situation after a few times.
When I say marine railways do this, they usually have catwalks with people on them so it there is someone there to physically throw the line over. The ones without catwalks use various forms of buoys or leading all the lines to a single point.