Whenever the Prophet ﷺ took a bath after Janaba he started by washing his hands and then performed ablution like that for the prayer. After that he would put his fingers in water and move the roots of his hair with them, and then pour three handfuls of water over his head and then pour water all over his body.  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّ النَّبِيَّ ﷺ كَانَ إِذَا اغْتَسَلَ مِنَ الْجَنَابَةِ بَدَأَ فَغَسَلَ يَدَيْهِ ثُمَّ يَتَوَضَّأُ كَمَا يَتَوَضَّأُ لِلصَّلاَةِ ثُمَّ يُدْخِلُ أَصَابِعَهُ فِي الْمَاءِ فَيُخَلِّلُ بِهَا أُصُولَ شَعَرِهِ ثُمَّ يَصُبُّ عَلَى رَأْسِهِ ثَلاَثَ غُرَفٍ بِيَدَيْهِ ثُمَّ يُفِيضُ الْمَاءَ عَلَى جِلْدِهِ كُلِّهِ  

(the wife of the Prophet) Messenger of Allah ﷺ performed ablution like that for the prayer but did not wash his feet. He washed off the discharge from his private parts and then poured water over his body. He withdrew his feet from that place (the place where he took the bath) and then washed them. And that was his way of taking the bath of Janaba.  

عَنْ مَيْمُونَةَ زَوْجِ النَّبِيِّ ﷺ قَالَتْ تَوَضَّأَ رَسُولُ اللَّهِ ﷺ وُضُوءَهُ لِلصَّلاَةِ غَيْرَ رِجْلَيْهِ وَغَسَلَ فَرْجَهُ وَمَا أَصَابَهُ مِنَ الأَذَى ثُمَّ أَفَاضَ عَلَيْهِ الْمَاءَ ثُمَّ نَحَّى رِجْلَيْهِ فَغَسَلَهُمَا هَذِهِ غُسْلُهُ مِنَ الْجَنَابَةِ