Wow I just learned that by doing L+R, put the cursor on EXT Onslaught(only once), and press triangle, the sword skill count up by 2 instead of 1. It also skips attack animation. Real handy for grinding sword skill implementation. Thanks gamefaq and GAF users. Bonus: You don't need to release L trigger.
I'm using it at "La Ulpuera Gardens" on insect egg near "Nightmare Beast", while doing quest to kill "Nightmare Beast" in Alevaste Otherworld Area[3rd quest in the list]. Best doing in solo multiplayer mode since dying won't lead to game over.