When the Messenger of Allah ﷺ performed the ritual bath after major impurity, he would call for a vessel resembling a milking pail. He would scoop water with his palm and begin with the right side of his head, then the left, then he would take water with both palms and pour it over his head.
أخبرنا محمد بن المثنى قال حدثنا الضحاك بن مخلد عن حنظلة بن أبي سفيان عن القاسم
كان رسول الله ﷺ إذا اغتسل من الجنابة دعا بشيء نحو الحلاب فأخذ بكفه بدأ بشق رأسه الأيمن ثم الأيسر ثم أخذ بكفيه فقال بهما على رأسه
Bukhari transmitted it in the Book of ghusl, chapter of one who begins with a vessel or perfume during ghusl, hadith 258, and Muslim in the Book of menstruation, chapter on the description of ghusl for janaba, hadith 318, from Muhammad bin Muthanna, with the same chain.