A candy thermometer is pretty much always the answer when it comes to candymaking, which includes caramelizing sugar.
Assuming the soft ball stage is indeed the best for brewing, all you have to do is keep track of the temperature: the soft ball stage is at 112-116C/234-241F.
While you can certainly buy specialized candy thermometers (they often have clips to attach to the pot), all you really need is a thermometer that's accurate in that range and can be easily dipped into your pot. (That is, don't use some old glass thermometer not meant for candy, but a kitchen thermometer with a metal probe is fine, whether or not it was sold as a candy thermometer.) Make sure that you have it in the liquid, not touching the bottom of the pot.
Note that this is well short of burning; there are several other stages hotter than that. So just don't use excessive heat, and keep an eye on it, and you won't have any disasters. This is also likely why people are a bit suspicious that this is the right stage to aim for: table sugar doesn't start browning until you're past all the candymaking stages, up to ~170C/338F. However, table sugar is pure sucrose, while honey has a lot of imperfections and is monosaccharide fructose and glucose, so it likely caramelizes much faster, so this may well be a good stage/temperature range.
There's also a way to test without a thermometer, but it's more difficult to get right on the first try. The stage is named the soft ball stage because if you take a bit of the syrup at that stage and drop it into cool water to quickly cool it, you'll end up with a soft, smooth ball/lump.
Adding water doesn't really help here. The temperatures are well above boiling, so the water is really just there to help get things going initially; the water helps ensure that there's something in contact with the whole bottom of the pot (no hot spots to form), and lets things flow around a bit, so you get to melted sugar with less fuss. Since you're starting with honey, you're already fine. Even if it starts out thick, it'll rapidly get thinner as it heats. All that will happen if you add water is that it'll take longer for all the water to cook off so that the temperature can rise to where you want.
Finally, this isn't what you asked, but if your goal is flavor, you can also simply heat slowly until it starts to brown/darken a bit and smell good, and then immediately remove the pot from the heat. The "slowly" is really important, because once the water is gone, the temperature will rise rapidly. You can still use a thermometer to help out with this plan, by watching for the temperature to pass 100C and start to increase more quickly; at that point you want to make sure the heat is very low and you're ready to move the pot.