Cleaning out the brine tank is a regular maintenance item if you own a softener. For residential situations we typically recommend once a year. For commercial applications where you process more water and go through more salt, once every 6 months may make sense. You'll figure out what frequency makes sense for you after you do it a few times.
Run your brine tank low on salt, and then pump it out or dump it if you can. Brush and hose it out. While it's empty, remove the brine valve and turn it upside down a few times to make sure you hear the little ball rolling inside the valve. Clean the intake on the valve. Reinstall making sure you have a leak free attachment of the brine tube to the top of the brine valve. Refill with salt and water to your normal levels and you're good to go.
Also don't forget to do the little bit of periodic maintenance needed on the softener valve.
Russ