Mishkat al-Masabih 435

‘A’isha said that when God’s messenger washed because of a seminal emission he first washed his hands, then performed ablution as he did for prayer, then put his fingers into the water and moved them through the roots of his hair, then poured three handfuls on his head with both hands, then poured the water over all his skin.
(Bukhari and Muslim.) In a version by Muslim he first washed his hands before putting them into the vessel, then poured water over his left hand with his right hand, then washed his private parts, after which he performed ablution.