Oberhasli,
The mixture of kasein and salt causes the slimy effect. To overcome it, add CaCl to the brine to ballance the loss of it from the cheese in the brine. Add a shallow ts of CaCl/1 liter of water. For feta I use the whey as brine with a rate of 16-18% salt. If it is too salty for your customers, recommend them to soak the cheese in water or milk before eating. Feta should be salty. I wouldn't use less salt, as it functions as a preservative as well.