Glyphosate, of course.
The patent has expired now, so although you can, if you wish, buy it at a high price under the trade name "Roundup" or "Resolva" you can also buy it under numerous other names, including "Glyphosate"
Own brands are cheapest. It is a generic chemical. Just look at the small print on the back.
A 2-litre bottle of the concentrate, that you mix with water before use, is better value than buying a small bottle of the dilute spray.
It is best to get a red watering can to apply weedkiller, that you don't use for watering plants and possibly getting chemical residues on them. A fine rose is suitable. A sprayer can be used but the mist is much more likely to drift onto plants or lawns you want to keep.
You water it onto the foliage, where it is absorbed. It doesn't poison the ground, and is inactivated by garden soil. If you are careful, and it's not windy, you can water it onto ground around shrubs, bushes, trees, roses etc.
