We use 2 on the farm
Ripper 480 & Grazon Extra
Against popular belief you mix it according to the weeds your spraying, too strong your waisting spray or the plants wont absob the poison. Too week well think of it like light beer....
We sprayed around a 7 acre paddock for a variety of weeds 2 weeks ago soft grassy type weeds ripper 480 mixed at 15mls/1L by the time we finished spraying they were starting to wilt, 2 weeks later they were completely dead and brown. Woody weeds like lantana & privot mixed at 25mls/1L at 2 week mark leaves are falling off and browning, stems are now brittle and shatter when slashed with the tractor.
Dont go to bunnings to buy poison go to Elders or CRT type farm supplies usually they keep smaller & large quantities, we buy ours in 25L drums.
Even for spraying of insecticides around the home to keep away spiders, roaches etc you can buy concentrates like Solfac which are safe to use indoors and outside and keep away nasties well.
Also when spraying wear protective clothing usually we wear a spray suit, goggles, breathing mask & latex gloves, once spraying has finished and we have cleaned up the equipment we hit the showers and have a really good wash. I saw the results of someone spraying ripper 480 without protective gear for about 2 hours and he didnt shower afterwards, he was badly ill for about 3 days vomiting, diarrhea, fever the works, now he suits up every time
cheers
Scott