I just read the Biography section of Earl Scruggs & The Five String Banjo. As a boy, Earl was exposed to several three finger banjo players, one of whom was Smith Hammett who Rick referred to. He tried very hard to emulate them, especially Hammett.

In the Book Bossmen, Monroe claimed that Earl's style wasn't fully developed when Earl joined the Bluegrass Boys, Monroe says that Earl developed some new rolls while with the Bluegrass boys and continued to develop after he left them.