That article was my main guide when I was setting up my brackish tank, very helpful. I use marine salt mix to mix up my water and a hydrometer to measure my specific gravity. Looking into getting a refractometer when I can spare the cash since I will be converting to full marine in a year or so, but since most brackish fish, including my gsp's, do fine with slight swings in salinity I don't need the extra precision. Be sure to know the range of salinity the fish you want needs and stick to that. Some need water closer to fresh and others need closer to full marine, and some have changing needs as they get older.
As for other water parameters it depends on the species you want to keep but many brackish fish like harder water and relatively high pH. My tank runs at about 8.2 pH. Crushed coral in the filter or substrate can help with buffering the pH and hardness. Hope this helps and welcome to the world of brackish fishkeeping!