Mainer's first recordings came in 1934 and are compiled on "Ragged But Right: 30's Country Bands". Mainer performed with The Mountaineers on tracks such as "Maple on the Hill", "Seven and a Half" and "Johnson's Old Grey Mule". Also included on the compilation are Mainer's later collaboration "Short Life and It's Trouble" with Zeke Morris, his solo effort "Riding on That Train 45" and a sample song "Mitchell Blues" from his band the Sons of the Mountaineers. Throughout his career, he was noted for his unique and innovative two-finger banjo fingerpicking style, which some view as a precursor to three finger bluegrass banjo styles. Mainer took jobs at local radio stations to increase the visibility of his relative's ensemble, recording classics such as "Take Me in the Lifeboat". During this time, he appeared on many regional stations including WBT in Charlotte, WPTF in Raleigh, WNOX in Knoxville and WPAQ in Mount Airy.