I have tried all kinds of drivers but this model "MFC-J6520DW" doesn't work on Solus at all. I add different drivers but nothing prints. I tried with cable and WiFi. May be this link can help for adding the driver from the official website.

http://support.brother.com/g/b/downloadlist.aspx?c=us&lang=en&prod=mfcj6520dw_us_eu_as&os=128