I really don't think SP is a requirement, just a handy way to indicate that you're near sleep. Concentrating on anything too hard is just going to distract you from your body's natural impulse to sleep.

I find that the easiest way to consciously slip into dreams is to relax (easier said than done obviously) and just observe whatever visions/sounds/feelings your mind concots. Watch them build up and there's a good chance you'll find yourself consciously dreaming.