Now this is a résumé: dapper king of Miami soul, groove-master songwriter for the likes of Sam & Dave, trailblazer of rap music, and the novelty act progenitor of both 2 Live Crew and Weird Al Yankovic. For the past 40 years, r&b legend Clarence Reid has been better known as Blowfly, a potty-mouthed, purple-hooded alter ego responsible for such crass classic parodies as “Hole Man” and “Shitting on the Dock of the Bay.” This affectionate, if occasionally leering, documentary reveals Reid to be an indefatigable performer, paranoid loner, and limping late sexagenarian who’s still the filthiest boy in the room. Having sold his lucrative catalog for a paltry sum in order to pay off debts, Reid teams up with road-hog percussionist Tom Bowker to wring a meager living out of the Blowfly legacy, which sends them from sparsely attended saloon sets to a sold-out festival show in Dresden, where our caped offender dodges projectile trash. Although its subject is never less than captivating, Jonathan Furmanski’s film is frustratingly unfocused, a scattershot collection of candid footage and biographical information. Thankfully, Blowfly’s world is weird as promised, a discordant mélange of hairnets, hissy fits, cock talk, and cockamamy fears of the feminine sex.