Yes, I've actually launched it by hand on a dolly many times.
I also talked with another owner who stored it on a dolly (they didn't own a trailer).
Once it's on the dolly, it's easy to launch/retrieve in the water (the dolly is light enough that it floats).
(The only hard part is transferring the boat from the trailer to the dolly on land, if you need to do that.)
The dolly is well-balanced, with the axle near the center of the boat, so it's pretty easy to retrieve on a flat beach.
But the boat is heavy enough that you would need two people to pull it up a steeper beach or a ramp.
The dolly handle is wide enough that two people can walk side-by-side while pulling it.
Years ago, Seitech was the only manufacturer of a J-18 dolly, but I don't think they're in business any longer.
It looks just like a larger version of a Laser dolly, but with two long tubes instead of one.
It uses standard Seitech parts, which are all interchangeable with other Seitech dollys.
I'm no longer using my dolly, so I'd be willing to sell it if you're interested.
I still have the original brochure if you'd like me to send you a PDF copy of it.
Sincerely,