As music journalists, we try to avoid using superlatives, like, say, “the greatest living blues drummer.” At the same time, it’s inarguable that for those who’ve been in a room where the Austin drumming icon George Rains is playing, the notion is tough to ignore. Rains’ credentials in the world of blues are impeccable. In addition to backing Jimmie Vaughan since 1993, he was the house drummer at Antone’s blues club for a decade, and has played behind just about every blues artist you can think of from the early ’80s onward.