To get really good wheel dollys you have to spend some money. We have a bunch of the Harbor Freight ones and they suck. The casters don't turn easily to redirect the car, and sometimes you have to take a ballpeen hammer and tap them to get them in the right direction. The wheels are also so small they don't go over irregularities in the pavement easily.

We now use them to put stuff like transmissions and rear axle assemblies on, they work ok for that purpose.

Don