You need to fold in the whipped cream so that it stays light and airy. A great way to fold it in is to use a rubber spatula because it is a very light material. The rubber will also be a great tool to scrape the bowl when you pour it into the crust. If you don't have a rubber spatula, a wooden or plastic spoon will work just fine, or even a whisk. Whatever you use, just be gentle with it.