I usually stick with 4% by weight of ingredients for my ferments. Sandor Katz says you can pretty much
do what you want. A
handy chart from fermentation recipes is one I've used in the past. Many here use starters such as whey or hooch from sourdough or probiotic capsules, and it is generally held that you can get away with less salt when starters are used since they jumpstart the ferment. Note that I'm not using brine; I blend the ingredients into a fine mash and add the salt to it. Here is a link to a
tutorial I posted a while back that may be of some use.
Please be sure to photograph your process and share it with us here - we love pics! Best of luck on your newest journey.