The most common agricultural use for Roundup is for the tall weeds that sprout up in the field. Many of the objectionable ones stick up above the crop plants, so the "applicator" is just a long horizontal pipe. A common sisal rope is threaded in and out through a row of holes in the pipe, and the pipe filled with the chemical. The Roundup wicks into the rope, and when it wipes across the plants that stick up as you tow the pipe above the crop, the "wetted" weeds die.

Spraying - as the jug at the garden shop will say you should do - wastes most of the Roundup, since any that hits the ground is almost immediately inactive and all that's needed is a small smear on a few leaves of each plant.

The Ag station nearby maintains "test plots" about a yard square of several dozen grasses and has used the "mop the barriers" method for at least 20 years that I know of, to prevent the grass plots from growing into the divider lanes.

Spraying may still be effective for a large plot in which you want to "kill everything" in preparation for a new "from scratch" lawn, but the mop works well for smaller areas - or "as long as your back holds out."

Do note that glyphosate has been in use for a ocuple of decades, and there are "Roundup Resistant" crop varieties available, and a few weeds that have spontaneously developed significant resistance. If you encounter a "leafy grass" that glyphosate doesn't kill, your best recourse would be contact your nearest Ag Agent for advice on what it is and what else will work on it, since the resistant plants vary a lot depending on location and climate. Some of the alternate chemicals are less "planet friendly" than glyphosate, and other methods may be preferable, so just randomly "getting a stronger chemical" isn't what I'd advise without help from an expert.

John