He achieved so not only by systematising kōan practice and teaching on the "great doubt", but also by promoting the practice of Zen for all including rural commoners, by opposition to the previous elitist approach of Rinzai. Until Hakuin, Sōtō was the Zen of the people, as reflected by the saying 臨済将軍、曹洞土民 (Rinzai Shōgun, Sōtō Domin) i.e. "Rinzai for the Shōgun, Sōtō for the peasants".
Among many methods, Hakuin notably used art to convey some teachings, often thanks to text embedded in scrolls he would give to some students, and sometimes with remarkable humour.
This 3'01'' video Bunkamura「白隠展 HAKUIN 禅画に込めたメッセージ」紹介 ロングver is from a recent exhibition in Japan on Hakuin's art (www.bunkamura.co.jp/museum/exhibition/12_hakuin.html).
For further information, I strongly recommend "The Religious Art of Zen Master Hakuin" by Katsuhiro Yoshizawa (with Norman Waddell), published by Counterpoint.