First cut some Comfrey (in my case, not a lot - yet), and chop the stems in to small pieces. Put them in a bucket, preferably one that has a lid.
Fill the bucket with enough water to comfortably cover the Comfrey.
Put the lid on. This will stop the mixture being diluted with rainwater. It will also reduce the smell, and the likelihood of small creatures falling in by accident.
Now all you have to do is wait. The Comfrey leaves and stalks will decompose quite rapidly (hence the smell), and become a sort of thick gloopy substance much more akin to soup than to tea. I find that making it in a bucket normally takes 3 to 4 weeks. The resultant liquid if rich in the sort of nutrients that are enjoyed by fruiting plants such as tomatoes, chillies and peppers - and probably Courgettes (as if they needed any encouragement). My chillies and peppers would certainly welcome a dose of it right now!
This plant is one of my Turkish Sweet Peppers. Its smaller than I had hoped it would be at this stage of the year, and so far it has only set two fruit. The battering it received at the hands of last week's hailstorm certainly didn't help, but since then we have had a fair bit of sunshine, so I'm hoping they will all buck up soon.
By the way, even if you don't have any Comfrey growing in your garden, you can often find it growing on roadside verges, where it is available to those who want it. Years ago, I used to go out foraging for it at this time of year, and the plants currently in my garden are descended from the harvest I brought home in that way. Comfrey roots very easily from stem-cuttings, so it is seldom difficult to establish a patch of your own.
When the "Comfrey Tea" is brewed, distribute it carefully around the base of your plants using a watering-can without a rose. If you use a rose it will rapidly become clogged with fibres. When made by my method it is relatively weak, so it doesn't need diluting.
I just wish I had more of the stuff, so I will be doing what I can to propagate some more plants.