Frank, like anything, the portable WS tanks need maintenance to keep the water soft. For example, how do you know when your water is soft? A key to using a portable WS is the use of water test strips (The Home Depot) that indicates the current level of water hardness. Let me take a step back.
The resin, the brown crystals you mentioned, are like small magnets for calcium deposits that are byproducts of some water sources. These deposits are what makes water hard. As water moves around the resin the deposits adhere to their surface and soft water is delivered. Eventually, the resin becomes saturated with deposits and the delivered water now hard. So you must "regenerate" the resin which chemically scrubs the resin pellets and allows the softening process to repeat. The regeneration process uses salt.
Through experimentation, I have developed a process for regeneration the seems to provide a deeper scrubbing of the resin and therefore a longer period between regens. I use a half gallon milk carton and add the salt to about 2 pints of water. Shake vigorously to develop a salt brine. Disconnect the water softener from the RV and empty it using the downstream hose connector. Do not remove the top from the tank or attempt to empty from the inlet hose connection as you will loose the resin. Get as much water out of the tank as possible. I actually blow into the inlet to pressure the water out. Now, take off the top and pour the brine into the tank, pausing to shake the milk carton solution to maximize the amount of salt. When brine solution is completely in the tank fill any remaining void with water. Now roll and shake the tank to help ensure all of the resin is exposed to the brine. I plan my regeneration cycles to coincide with when we're going to be gone for a few hours and let the tank soak in the brine.
Now, it's time to flush out the salt brine. I connect to the water source and slowly push water through the tank while using a section of hose to divert the flow and prevent the salt from killing plants or grass. Using my self-calibrated rate of flow, it usually take about 10 minutes to remove the brine. Brine is gone when the water passes the taste test for salt-free taste. Reconnect the tank to the RV and your done. Whew...that was a lot of work! Now sit back and have a beer.