I completely disassembled it - pulled the logic board, etc - then submerged the circuit boards (logic, ram, magsafe) one at a time in water and used a toothbrush to brush off all corrosion and dirt, then used compressed/canned air + hairdryer to dry each component, then reassembled once all surfaces had appeared dry for 12 hours. Maybe I should have used distilled water for the cleaning...?