Need tips for whipping sour cream

I have a recipe that uses sour cream and sweetened condensed milk as frosting, provided the sour cream has at least 20% milk fat. I have 30%. However, I have noticed that it does not whip like regular whipped cream. It first sort of thins out, then thickens again. However, does anyone have any tips or tricks on how to ensure the thickening happens just right? Last time it seemed a little too thin. Just wondering if there is something I must always do, or can do to improve my odds. For instance, with whipped cream you can over beat and get butter. Can you over beat sour cream? Help would be great! Thanks.