My measurements were 6 feet wide by 4 feet high and 16 feet long
Some 2x4s and plywood, heavy plastic.
Build it around the car and start filling.
It would only attack the rust so it would be very reusable after.
Imagine 400 gallons the rust that can be removed!
On a side note...
I have discovered that if I take the used Evaporust and keep it separate from the new I can get much more life out of it.
I use the old for the heavy rusted stuff then use some new for the last amount of soak