one's by the gas meter have already bought the farm. Just watch those others and like I said, if they aren't died/dying back after a couple of weeks, get some more and hit them again. If cost is a problem, you might look at Spectracide's version of roundup. The main thing is you want to make sure and buy total kill product for vegetation. Just don't get the kind that kills the soil, too. Otherwise, you won't even be able to get grass to grow for about a year.
As for the rocks, it's a good idea to put something down first. That is, unless you just like pulling weeds! LOL! I know I sure don't! Like she said, even just a garbage bag will help, just something to stop seeds from making contact with soil. Look at it this way. Weeds are tenacious buggers and will come up in concrete if given a chance. How many times have you seen something growing out of the crack in a sidewalk? I know I've got cracks in the concrete top on my cistern and weeds are growing out of it. I even had to roundup it! To me, it would just be alot easier to put something down to try to keep them out to start with as opposed to having to mess with them after they get there. But you know your situation and I don't, so use your own judgement. Anyway, congrats on your weed eradication success! Fivecat