Continued:-  The good thing is that it doesn't harm the soil, and is not harmful to humans or animals (if my population of rabbits is anything to go by).  However, it should not be allowed near ponds etc. as it can be harmful to aquatic life.  Also, do not let it anywhere near any valuable plants as it's non selective and will kill those too.  Always spray when the weather is dry and windless.  For application, use a backpack sprayer (mochilla).  The barrel shaped ones with a handle on top are only any good for small areas as you need to keep setting them down to pump them up whereas the backpacks you can pump with one hand as you walk around.  They are around €30 - 40.  The Ironside ones that Cifec sell are good.  I have a 15 litre model but it can be a bit heavy when full and I've taken to only refilling with 10 litres so you'll save a bit by getting a 10 or 12 litre model.  I would estimate that you will need to respray about three times a year.  There's another type of weedkiller availabe known as "capa" (ask at the co-operative.)  This will keep the weeds down for a whole year as it prevents re-emergence BUT do not use this on areas that you intend to cultivate as it can remain active in the soil for up to four years.  Hope some of this is helpful.  If you have any questions then fire away.  If you have a huge area to treat and feel that even a backpack is not the answer, I can put you onto an agricultural contractor with a tractor and boom sprayer who will charge by the hour (probably about €30 but I can check) and you supply the herbicide).
For what it's worth,
Bigyin