I really don't know what you mean by salt build up. If the rez gets a little too stron I add water. Little too weak, add nutes.
If you have the ppm dialed then it should stay pretty damn stable.
So my system us basically ebb and flow, but reversed.
200 gallon rez for 16 10 gallon trash cans. It takes about 100 gallons to fill all the buckets so 100 left in the rez.
The rez is chilled to 65.
Once an hour all the buckets empty into the rez, the returning water is about 67 and the buckets are filled back up...water now 66.
When there is only about 50 gallons or so in the rez I empty the buckets into the rez, add water and nutes till its full again and I'm done.
The large volume of nutes helps buffer swings and regulate temps.
I do NOT have dead roots or salt build up. If you have salt build up your nutes are too strong. Water and nute uptake should be balanced.