In article , davidlobsterpot601
@hotmail.com says...

Looking at the years of buildup of crud underneath the 'skirt' of my
electric Flymo,

Just let the crud get dry (turn Flymo upside down in the sun)
then insert the corner of a paint scraper to open a starting hole in
the crud; once you can slide the blade between the plastic and the dried
buildup, it's easy to ping off in large chunks.

Janet