Stylobb,
Hong is right on the 双拼法. A bit like phonics, breaking the sounds down into 声母and 韵母. In Hong's eg, the 声母 'b' forms the initial sound of the word, whereas the 韵母 'ai' forms the 'tone' of the word.
When you teach the word 白 with 双拼法, the kid will learn to say "bo-ai" = "bai", bai1, bai2, bai3, bai4. This way they will also know the 声调. This was how I was taught.
I'm not too sure how 直呼法 is taught. I reckon the kids don't break the word down like that, they just memorise the whole pinyin as a word.
Hong/Cherly,
CY's HYPY tingxie comes with the characters as well. In P2, he is supposed to write down both the Chinese characters and HYPY for tingxie.