I use the second method , the first stikes me as too fiddly.
One trick we have found was after you do the rough cuts, put the fillets in the fridge once cooled the meat cuts eaisier.
I have a habbit of cutting out the belly meat before cutting the fillets that way I only need to think about a clean cut along the back.
I don't bother keeping the fish finger attached, if I am cleaning for immediate usage the fish fingers get pooled and ground for patties.