What was Bud's trick to falling asleep?

In Chapter 8, Bud and Bugs spend the night at a Hooverville in hopes of catching the morning train to Chicago. When Bud lies down, he does a little trick that helps him fall asleep. Bud takes his blanket out of his suitcase and pulls it all the way over his head. Then Bud takes a deep breath with his head buried underneath his blanket. He breathes deeply and smells three more times until the smells of his surrounding environment are gone, and all he can smell is his blanket. Bud mentions that the smell of his blanket reminds him of how his mother used to read to him before bedtime. As he closes his eyes, he imagines that his mother is reading him bedtime stories until he starts to dream, and gradually falls asleep.