You actually get more control the way described; holding it your thumb & two first fingures. But, you need a strap, or a table thingy to hold the Tx still. You'll notice all the pros have a neck strap, and don't actually hold the Tx..

Flying with your thumbs is easier, but the skin on your thumbs is loose, and while you may think you're moving the stick, You're actually moving your thumb bone inside your thumb skin... or that's the theory at least! Not to mention, you are actually holding the Tx..

Learn now, with your thumb and forefingers, as it's harder to re-learn later!