Khoi,
I usually do it like this guy. Do it in the summer so it roots faster.
https://youtu.be/Qa43Bn8L3hU
That guy's pretty fast with his special wrapper that holds its shape and moisture at the same time. Long fiber sphagnum moss is the best material to use.
For me I mix 50/50 perlite and peat from home depot or similar. Or get the already mixed bag but it's more costly for the volume.
Add water and squeeze out as much as I can. Put a fistful into my plastic bag. I use the air bags that come with products I order online. Cut diagonally one side so that when I wrap it around the branch along the cut, I can fit one half with the medium into the other half that's just empty.
Tie a knot with twine around the lower end of the bag to the middle of the woody part and wrap the twine around the bag and branch while distributing the medium around the branch. Make sure to close the top end of the bag with a couple loops around the branch. Tie it off when you run out of twine. I use 2 arm lengths of twine and try to get the best seal I can so it doesn't dry out too fast.
Put aluminum foil around the plastic to block out light. Try to get it tight so ants don't go in and nest there. Check every so often after 2 months for roots. Cut it off when it's half full of roots. You can get away with a little less roots with guava.
I can take photos later if you want. I still need to do some citrus and camellia. They do take much longer in cooler weather. I'll have aluminum balls on my trees.