Relationship Rewind - Deaths Door

Question about this.
Say you are at deaths door and you have done the opposite of not chasing. And are now in the indifference stage.
How can you get bsck from this.?
In the book he doesn’t really talk about how you can reverse it if shes blocked you. Say you didn’t give space after the break up.?

What action must you take?
So shes blocked you, made it clear its over … still in pain but wants to move on. Do I do nc and then send the magic letter? Despite chasing like a mad man.

Would appreciate some advice

Also this magic letter goes against the advice given on this site with the post NC message you send ie. In not talking about your feelings. Which the magic letter clearly does

What’s better to use? Magic letter, or casual msg?

I’m confused. Even relationship rewind talks of casual msg and a magic letter in deaths door.
But not clarifying which is best to use and when