There are multiple opportunities for every monster to land Lv3 charges. When using a greatsword, it's important to know what the monster might/will do next and place charge attacks ahead of time. If you're new to MH, it's probably not the best weapon to use, but I used them at first too, and they're still my weapon of choice.
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For a Qurupeco specifically, there are a LOT of opportunities to land an L3. When he's calling another monster, when he's singing, when he's dancing, etc. It's easy to knock him out of the air, and follow up with an L3.
It's tougher to land L3's on a Great Jaggi. He doesn't spend a lot of time idle. He's easy enough to kill quickly with just draw attacks, though.
BTW, I don't recall SD's videos being remarkably helpful with regards to learning to L3 charge.
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