Everyone has a little bit different way of doing it, just practice on your own car and see what gets it done faster, some use different soaps, D/I water, some brush, some don't. There is a list of things. what kind of fleets are you looking at?
They are alot of depends in your Q'tion,alot of different setups and the way several control run off.
If you would post your rigs gpm the members would have more of a ideal as to tell you about speed.Don't know if the best efficcient way is the best way b/c of to many efficcient ways for each job at different job sites.
just starting!!!! 
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