Here's some stuff past me didn't figure out:
The opening I had in the previous post was a bit scuffed and awkward. Attachment 1 is a slightly faster and more consistent version of it. As long as your jump is after the second twig and last pogo is after the rightmost edge of the rightmost bush, it should hit the Skarrgard. Due to random inconsistency during pogo dashes, you may be much higher or lower than I was in attachment 1, but nearly anything works. All of the attachments use this opening, so this variation can be seen between them.
You can actually hit the Skarrgard an extra time during it's swing. This lets you kill it super fast if you get the perfect rng of 3 swings in a row (attachment 2).
The only reason for an upslash before a jump or burrow is to avoid the knockback of a regular slash - don't bother upslashing on burrows. If you find it hard to avoid getting hit by walking under jumps, you can just not slash before a jump and focus on the movement, or you can do a slightly tricky parry (attachment 3). It's really hard (but possible!) to actually hit the Skarrgard with the parry, so try to focus on perfecting the timing before that.
Other than all that's it's straightforward. If you're just trying to survive, try to work on perfecting your responses to attacks and then recognising them in the context of the fight. If you're trying to go as fast as possible, you can work on adding the harder strats