If you only need to type a single number, you can tap and hold the .?123 key at the bottom of the main keyboard, then drag your finger to the number key you desire. When you release that key, the number will be inserted, and the keyboard layout with instantly switch back to the main ABC layout. This eliminates the need to tap the ABC key again. The tap and drag trick always works with any other key in the .?123 layout.
And yes, I'm able to touch type on my iPad too.
For long typing sessions, I found myself putting the keyboard on my lap while placing the iPad off to the side—sometimes not even in direct eyeshot. For longer writing, there's a sort of freedom that comes from not even looking at the screen while you type. (My friend Quinn Norton said that on longer writing jags, she sometimes uses her wireless keyboard in a completely different room from her computer, a sort of modern twist on the big-keyboard-tiny-screen experience of early laptops like the Epson HX-20, which were for years favored by some journalists even as laptops with larger screens were commonplace.)
I've read similar tips in the past where people suggested turning off your computer monitor.