If you want to have exactly the same effect as using renewal you want to maintain your salt level at about 3200 ppm using ordinary water softener pellets or solar salt (not rock salt) that is at least 99.5% pure and has no additives for rust removal or cleaning the softener tank, etc. (I use the solar salt because it dissolves faster). You want to make sure you maintain the CYA close to 80 ppm since you wil lose a bit of both salt and CYA each time you backwash the sand filter . Finally, the 'magic' ingredient in Renewal is borax! Maintaining a 30-50 ppm borate concentration in the water, combined with maintaining an uncorrected total alkalinity of 70-90 ppm will help increase pH stability, reduce acid consumption, lessen your chlorine demand which will increase your cell life, and will act as an algaestat! Good stuff!
If you figure out the cost of using Renewal vs. using solar salt, borax (20 mule team!), cya and a bit of acid to compensate for the pH rise from the borax you will find it will save you a LOT of money over Bioguard's propriatary blend of salt, borax, dry acid and stabilizer!
If you want to learn how to do this just ask and we will tell you!
If you prefer to just use salt and CYA that is fine also but the benefits of also using borates have been documented on this and other forums many times over! I use them in my own pool.
BTW, the Mineral Springs SWG is a rebranded AquaRite unit. It's a very good SWG!