I use a set of Cat Trax on my wave and 99.9% of the time I'm doing it solo. The standard Cat Trax has an aluminum axle with a black rubber sleeve where the hulls contact it and the sleeve acts like a roller. Makes it real easy to roll the wheels under the boat, but difficult to keep the boat centered and squared on the axle. I lift up the bows and push the wheel under.
I was considering getting cradles to keep the boat positioned on the wheels, but wondered if the cradles would make it harder to load the boat. While I was trying to make up my mind about spending the $ on the cradles, I came up with a solution that works for me. I have a third line coming from the middle of the axle to the rear cross member, I then pass it through the cleat for my traveler. This 3rd line keeps the boat in place and I have no problem moving it around by myself.
One other hint is to get the boat in place and mark the lines where they meet your tie-off points (I use the side stays). This way when loading the boat all you have to do is line up the marks, tie off the lines and push the wheels under the boat.