Firstly, you don't have to go through an endurance test if you want to LD.

Don't worry about your body, don't worry about shifting position, it's naturally comfortable -- you don't need to analyse that, your body knows what's comfortable so let it be and don't bother about interfering.

For myself, the feeling of sleepiness is what to get lost in. Just feeling...it's hard to explain what I mean.
The feeling of falling, the feeling of spinning, rotating, drifting. The sinking or expanding feeling. The shifting feeling, getting lost in it. Other people who use very 'feeling' techniques may understand what I mean. The very motion is the transition.

Just lay down, don't try to remember the words, nor repeat them.
Just understand and do.

Lay down and let your body be as it is, let your eyes close. The only hard part is thinking that it's hard, the complexities you put yourself through for such a simple thing as closing your eyes or laying down -- just going to sleep, such a natural mechanism and there's no need to interfere with it, be with it. Follow what happens, there is no chance you can't lucid dream. It's so easy and simple.

Consider in steps, but when doing it, just do it, don't consider.
1. Be normal, just start letting your body drift off.
Relax, this is just going to sleep. For now, don't bother with thoughts, just feel yourself getting more and more relaxed, you're naturally falling to sleep as you've done every night.
There comes a plateau of relaxedness, a nothingness of your not-interfering. This is meditativeness.
2. Fall. Down and down you're falling and falling, or spinning, or rotating, or running. You can feel that feeling.
3. The transition continues following the motion, the motion becomes it, transforming. You can feel a sudden overwhelming acceleration, your senses coming very alive. You're in the dream.

Your body leads you through all these steps without you having to do much, just minor pushes in the right direction, you don't have to worry so much about the steps, they just happen with the feeling.