I have done barleywine with Brett C and its still has some viscousity . It was 1025 after primary and around 1015 after 6 months on brett C. Brett B has higher attenuation i think . Try brett C and mash at 68C . I think the flavour is a bit more in style of RIS . You will get old books, leather, sherry, port . Unless you use some aromatic hops in late additions.