How about killer mulch? You could put down six inches of
wood chips in your paths. That will smother anything underneath and its coarse
enough that stuff probably wont germinate even when birds
poop out seeds right on top.
As far as ground cover, what kind of weeds take over around where you live (other than poison oak)? If i were trying to push out a weed in the PNW for instance, I would sow
dandelions, plantains or clover. They are all near impossible to get rid of, low growing (wont compete for light if your growing them in paths) and best of all, don't sting. Mint would work too, but it will eventually creep into your vegetable beds, even if you grow it in the paths.