[HayZee518]

if this chimney shares the flue with some other device then it really don't matter on the smoothness as any creosote will form above the outlet. maybe some will fall back down but it'll be below the heat so it won't ignite. shove anything non flamable up inside the chimney and cement it shut. most modern chimneys have a separate flue for each device, i.e. hearth, woodstove, coal stove, oil burner etc.