Personally I prefer the old car tyre filled with diesel approach-not that I would ever do that you understand.........
Must be VERY satisfying watching the dam things burn.
The mobile ones I have had visions of anti tank rockets but that could hurt the operators. How about a flat bed truck with a high pressure hose on the back-as you drive past they are concentrating 500 yds down the road when WHAM suddenly it's raining very hard-inside the van.
John