I got some detangling spray which also seemed to prevent too much matting. It's belpher or whatever that brand is. Ddog didn't like me spraying it on him so I spray it on him and run it through his coat. It's got almond oil in it. Otherwise... Hairnet?
Not very familiar with ST type coat, but in general grooming terms - it sounds as if you are grooming regularly enough, but just in case - when you are doing it, the areas that tend to knot the most are behind the ears, behind the 'elbows', so special attention to those.