Glyphosate

360 is covered by regulations of use and should not be applied via a watering can. Using a higher amount is what's classed as poor practise. Run off should be avoided.
When you do the training you are taught about drift and weather conditions that a pesticide should be used. You should be able to calculate the amount needed for an area via your equipment and all usage will be documented.
One of the best methods that uses the least amount is where the product is used neat via an atomiser but the equipment is expensive.
Common mistakes are mixing a higher than needed dosage, appling too much and applying in poor conditions.
This product is also used for road side spraying and the better companies use sensor equipment that releases on the weed only thus cutting down on both the chemical usage and environmental impact.
For general use a hood helps, as do weed wipes that you simply wipe over the plant. Lots of ways to cut down the impact on the environment for general use round domestic settings.

 

You can always use this when you running out of weed killer

 

First attempt to deal with anything is nearly always brush application, the watering can's mainly used for a large area of hardstanding between 2 other properties with their planting right up to the boundaries, and the 360 is always diluted to the same strength as weaker stuff from shops/GCs is diluted to.