He's doing it. All on his own. After doing lots of strength exercises and stretching and the like, yesterday it just clicked. But he still wanted to hold onto hands.
Then today he did it. He just let go and went for it. It was beautiful.
By the way, the reason for the scream? We have this little game where we call each other "Pooch" and kind of playfully spank each other's butts. Well, Bini doesn't know the difference between a butt and a vagina apparently. Because I was expecting him to hug me in excitement and instead he pooched me in the nether region. He was so happy all I could do was scream (in shock) and laugh (in joy).