Here's my current solution for doing it solo. It's a multi-step process, but not too challenging and not fatiguing on your body.
See photo below.
1. Hook up ropes (with loops about 1-2 foot or two apart).
2. Hook rubber straps with S-hooks to the wheels and then attach them to the ropes with good tension.
3. Go to the front of the boat and lift up. The tension from the rubber straps will automatically pull the wheels under the boat.
4. Then readjust the tension by hooking the rubber straps further up the rope.
5. Repeat until you're the wheels are as close to the side-stay connection points (boat's center of gravity) as possible.
6. It's best to ditch the rubber straps at this point and secure the wheels with rope. (Not doing so you'll find challenges as you're wheeling it down or up the beach because the rubber straps will stretch and will thus come out a ways from the center of gravity, making it difficult to maneuver.)
The key to solo-launching is to have the wheels directly at the center of gravity. It will make you chuckle with how easy it is to move the boat.