Brake parts cleaner does a J O B on weeds. I use the Walmart brand at $2/can.
It evaporates quickly and if you use the small diameter red straw they comes with it, it allows you to easily direct the spray on the weed. It will be dead within 3-4 hours.
It also works wonders on insects too. Had a rather large (>2") cockroach in the garage (see pic) that I managed to get in the hole in the front yard for a soon to be planted tree. It had a hard time climbing out of the hole as the dirt crumbled as she (had to be right?) climbed the side to escape. Well, a quick shot of BPC and in 15 seconds (yes, you read that right) it was long gone sally with legs pointing skyward and not a movement to be seen.
Eddie