If you're serious on getting the right look, then a few practice shots to get the feel on how it goes on would be a recommendation. Get a feel on distance and how it stands up.
You can easily fly thru a gallon or more to do an undercarriage/wheelwells.
1 gallon probably might be a close call.
As far as the gun, you don't need anything fancy.
I used a gun I bought off Ebay and it did great.
I still have it if you're looking for one to buy for cheap.