Eyeshields, Gloves, Quality filter mask and throwaway overalls and a duckboard to stretch from side wall to sie wall don't sit it on the roof it must bear on secton over walls or you'll go through the roof. clean the roof with a short hair stiff yard broom or srcubbing brush.
Tape large holes and or splits with Flashband tape using the primer to bond the flash band laid with heat.
Then using and old soft hair broom coat the roof with Aquaseal Numb 5 three coats allowing each coat to dry. You may have to re-coat in approx 4-5 yrs, just keep eye on it.
Alternative is to have it removed by specialists [Local council must be notified]. for UK residents.
Bob, March 2009