I did, mate, but it was a hefty question with many pros and cons.
My advise is, if you're going to work from a car, don't go for a trolley (if anyone disagrees with me; please state your case; I won't argue), get a backpack and do 'tops only' mostly.
At first you'll use loads of water; say 200 liters a day; because you end up rinsing two, three or four times due to your inexeperience.
After a few months you'll find 100 litres a day (four barrells) will see you through a heavy day's work.
The backpack is suited to guys who want to work from a car and you're not filling it up all the time; and when you do it's quick to do.
There's a knack to the backpack though; and even after using it for nearly a year; I'm still finding better methods during my working day.
But, if you've got the money, get a van-mounted system and supplement it with a backpack for those hard to reach areas.