I frequently fish alone and use launches where there are no other fishermen lurking around which could give me a hand. I am sure there are better ways of doing this but this is mine.
All gear in boat, keys in boat ignition, back into ramp but not into water, insert drain plug, remove tie downs, remove winch line and safety chain, attached line from front of boat to dock post (next to ramp) watch that tie rope does not get under boat trailer tires as you back fully in. Move quick enough in reverse that boat floats free of trailer. Line keeps boat from floating away. Pull vehicle out, secure boat to dock, park vehicle, go to boat and limit out fishing.
Really the tricky park is the line to the dock from the boat, start fairly snug so as you back up and develop slack in the line it does not get under wheels or hung up somewhere on trailer.
Let me know if this is helpful
Rick