Question

how does walt whitman emphasize the value of the individual

Answer 1

SparkNotes' analysis is fairly concise and helpful:
"Throughout his poetry, Whitman praised the individual. He imagined a democratic nation as a unified whole composed of unique but equal individuals. “Song of Myself” opens in a triumphant paean to the individual: “I celebrate myself, and sing myself” (1). Elsewhere the speaker of that exuberant poem identifies himself as Walt Whitman and claims that, through him, the voices of many will speak. In this way, many individuals make up the individual democracy, a single entity composed of myriad parts. Every voice and every part will carry the same weight within the single democracy—and thus every voice and every individual is equally beautiful. Despite this pluralist view, Whitman still singled out specific individuals for praise in his poetry, particularly Abraham Lincoln. In 1865, Lincoln was assassinated, and Whitman began composing several elegies, including “O Captain! My Captain!” Although all individuals were beautiful and worthy of praise, some individuals merited their own poems because of their contributions to society and democracy."
http://www.sparknotes.com/poetry/whitman/themes.html

"Song of Myself" is the Whitman poem most often linked to the theme of individualism. Also, "I Hear America Singing" and "Poem of the Body" are great examples.