We use a very small, flexible, soft rubber kitchen spatula. You can buy them in a package with all sorts of sizes, The smallest one is perfect for opening a hatchlings mouth nice and gently. We just introduce it in the side of the snake's mouth, slowly turn and bingo...they open their mouth, the spatula keeps it open and it's soft enough to do no harm if used gently. Then it can be disinfected aftewards.