Yo! That would be me. I spent some major time on this issue.
Wheel dollies present a problem in how to get the boat up on to them. Issues abound with trying to drive up on to them or having to jack up each wheel to get a dolly under it. I even thought of trying to design something myself.
However, after a week or two of calling around, someone recommended go-jacks (dollies/jacks combined). They are expensive but I found some for $100 each, $400 total for a double-axle trailer. Costly but after 6 months of use they are well worth the convenience. Just get them under each wheel, pump them up a bit and then push the boat around the garage wherever you need it. Work like a charm. http://www.tooltopia.com/index.asp?PageAction=VIEWPROD&ProdID=11011