Short answers, pulled from the story.
Jelly Roll Morton credited Joe Sims of Vicksburg, Mississippi as the creator of scat. Gene Greene recorded scat choruses in his song King of the Bungaloos and several others between 1911 and 1917.
Louis Armstrong released Heebie Jeebies in February 1926 during a performance with his band The Hot Five. This recording became a national bestseller and established the foundation for modern scat singing.
Betty Carter was inclined to use sounds like louie-ooie-la-la-la which are soft-tongued sounds or liquids. Sarah Vaughan would prefer shoo-doo-shoo-bee-ooo-bee which uses fricatives, plosives, and open vowels.
Ward Swingle took the scat singing idea and applied it to the works of Bach creating The Swingle Singers. This approach pushed jazz singing nearer to avant-garde art music.
Many hip hop artists and rappers use scat singing to come up with the rhythms of their raps before filling in words. Tajai of the group Souls of Mischief states that sometimes his rhythms come from scatting and he usually makes a scat kind of skeleton before filling in words.