it's pretty easy, I mean, I guess it depends how long it's been, but you take a scuba tank, fill it up, get another one, fill it with gas, rig them so the system pressure feeds into one hose, and that hose leads to a pointable nozzle, have a wick on the nozzle, and whenever you open up the system WHOOSH flames everywhere.

You can make napalm with equal parts frozen concentrated orange juice and gasoline. I forget what the ratio is for sawdust. The trick is to light lots of things on fire while you're murdering plants, so you still have fire to keep them at bay