Is there a trick to thickening things with tapioca flour? The one time I tried substituting it for cornstarch in a recipe, the tapioca flour formed stubborn little blobs that just looked curdled and never would dissolve. But the box from the tapioca flour says that it's a good replacement for cornstarch, so I am wondering if there's a technique that I am missing.

(Is it OK to ask this here? If not, please ignore or redirect!)

-Valerie