A 10g tub of quality flux, also known as soldering paste.
This has a wax-like consistency and is easy to apply from the tip is a small screwdriver.
Not everyone will have soldering experience and if that is you, please read the five steps below and the notes on picture two.
1. Clean the surfaces to be joined if necessary.
2. Apply a small amount of flux to the area of soldering.
3. Heat using the flame of the butane torch and place the two items together.
4. Apply the solder to the heated brass while maintaining the heat until suddenly it runs.
5. Quickly remove the heat.
Practice makes perfect!
The tub will last you a long time because so little is used for each soldering job.
To solder, you will also need a small butane torch which can normally be found on eBay.