I bought the special mits from costco, they're water proof inside. One side is white the other is grey, the grey is meant for the wheels whilst white is for the bodywork. Its a bit like those cloths with ar$e and face on them.

I clean 1 panel at a time, once the panel is done I use the hose to clean any dirt out of the mit and because it's white you can see it come clean. I then put back into the bucket to get some wash solution and move on to the next panel. A superior method to the two bucket one IMHO