To the best of my knowledge (and it may be partial in this case)
belt dressing is for flat belts with slightly crowned pulleys where
sufficient tension may not be available to keep the belt functioning.
On V-belts, especially if much heat is involved, it can begin to
act more like a lubricant.

Generally if belts and pulleys are clean and normally tight, they
work pretty well. But I did go through a spell in Panama where all
the components of my 164's electrical system were apparently OK but
it would not charge. No belt squeal was ever heard but tightening
the belt tighter than I thought it would have to be solved the problem
after many disassembly/reassembly cycles over a period of weeks.
--
George Downs, Bartlesville, Heart of the USA!