The method that is commonly used is to puncture small holes in the interior diaper to allow drainage into the outer diaper.
Don't make sword like slashes because the inner diaper will not do its job of absorbing the most of flow.
Make many small holes that are perhaps toothpick in size to create the right amount transition.
Use of small pads or wash cloths while adding bulk can also keep the liquid flow from exiting out the leg holes of the waterproof diaper cover.
Trial and error till you find the right application.
Realize that the combination of diapers can only hold so much that a change maybe required - this probably with over night wearing.