I doubt that holding the cowling in line with the end of the runway will have lifted the nosewheel completely off the ground. It may have just fully extended the suspension. The wheel may still have 100lbs of weight on the ground, dependant upon the engineered pre-load of the suspension strut, plus the weight of the wheel.
You'll know that you have the nosewheel right off the ground, as once you're rolling, you'll not feel the ground vibrations through the rudder pedals. Both of the 182's I recently flew (a 182M, and 182T) could have the nosewheel lifted clear of the ground, and the runway still visible over the cowl - just. That said, I'm 6'3", so that improves the view a little.
One of my clients (the 182M) have just installed a brand new prop, after damaging the tips of the previous one. He told me that he flew gravel runways on occasion, so I was demonstrating the technique for best prop preservation: Full nose up control held, slowly open the throttle, allowing the aircraft to accelerate, and only releasing back pressure when the nosewheel could be felt to be off the runway, while maintaining a view of the runway ahead.
I agree that this is an extreme technique in terms of nose up, but the plane will do it if you command it, and it is your best chance of preserving a prop. I've only damaged a prop once, and that was in 1979, in a 182M, departing from gravel. I paid the Re n Re, and repair cost for the prop, which back in the day was hard on my finances - I learned. Since then, I've never damaged a prop in 4000+ more hours in single Cessnas. I meet owners who seem to think that props are a consumable. Well, if you can afford it, McCauley, or Hartzell would be happy to sell you a new one, but why not just save the money and down time, and fly the plane so as to not damage the prop in the first place?
The "Boeing" Cessna instructors perhaps don't think of this, as the Boeings they want to fly (excepting a properly kitted 737) are not gravel runway approved anyway. But Cessna
do operate from non hard surfaced runways, and pilots should be applying techniques to preserve propellers.