With my steel-bored 20", I get .5" groups at 100 yards, which is good enough for a non-contest shooter like me. My break in method was to go to the range and shoot about 100 rounds through it. Then, I took it home and cleaned it. Finally, I put it in the safe, and there it sits until the next time I take it out. [;)]
My 16" M4gery was broken in similarly: took to the range, and shot it. A lot. Accuracy on it is not as good as the 20", but that's due to barrel length, and not any break-in method, or lack thereof.
My opinion on this subject is that unless you're going to be shooting hamsters at 400 yards or doing competition shooting, I think you can just shoot and clean at the end of the day and have decent accuracy. I'm not saying that this is good for everyone, but it works for me.