I make a lot of fermented food. This guide complicates things a bit. You don't really need an airtight container with a fermentation lock. The easiest thing to do is just keep a layer of brine above the top of whatever you are fermenting. I use mason jars of all sizes and flip the lid over backwards and put the ring on loosely. This allows any gas to escape and keeps contaminants out.
Your method works, but to make it easier to keep the food below the brine, I put a tiny bowl (like you'd use for spices when prepping) inside the mason jar to push things down while still allowing it to bubble. Cover with a piece of cheesecloth and a rubber band.
Food below the brine is key, it will mold otherwise (as I've learned the hard way...).
Nipples are dandy, but one overlooked and very simple, effective method is a foodgrade plastic bag (sandwich, ziplock) placed over the mouth of the jar and held on with a rubber band. The flexibility of the rubber band allows gas to escape and if paranoid about the top layer, a leaf or more of cabbage (or something else) can help press the desirable layer beneath the brine. I've found that after 10-14 days the leaves become unappealing but do not affect anything beneath. Note: I ferment in Florida, with the AC rarely below 80f unless such occurs naturally. I have learned to increase the salt and decrease the time when the temp is above 77f.
Yes for sure, I need to upgrade my system at some point. Another one I've used is a ziplock bag partly filled with water. I don't love the idea of plastic in fermentation, but it has worked in a pinch.
I wish that worked for me, I've found there are folds in the bag that seem to be good starting points for mold/infection. Unfortunately I'm not certain what in my process caused this, after a few tests I decided it wasn't for me.
The Noma Guide to Fermentation mentions using a vacuum-sealed plastic bag. I find this much easier to manage. You will only need to "burp" the bag by cutting a corner off, releasing the air then re-sealing.
The vacuum sealer uses heat to seal special bags. You re-seal the same way you seal it originally by placing the part of the bag with a corner cut off in the machine and turning it on. The bag will get a bit smaller each time, but even for long ferments I don't need to do it more than 1 or 2 times. I just make sure to size the bag originally to account for it.
Our vacuum sealer said to never use it on bags with liquids. I'm guessing that's just a stupid compliance rule in case something goes wrong and it sucks the water into the machine.