this is just the main riff i figured out
played slow and bluesy of course

-----------------------------------------------|
-----------------------------------------------|
-----------------------------------------------|etc.
------------------5----------------------------|
--------7-5---5-7---7--------------------------|
-0----------7----------3----3-5-3-5-3-5-3-5-0--|

sometimes switches up like:
---------------------------------------------------|
---------------------------------------------------|
---------------------------------------------------|
------------------5h7p5----------------------------|
--------7-5---5-7-------7--------------------------|
-0----------7--------------3----3-5-3-5-3-5-3-5-0--|