Swift step requires a bit of technical setup but the execution is straightforward once you understand the timing. Work your way through orange-marked activities around the map especially focusing on lost pages and kuji-kiri meditation spots since these give knowledge points faster than most other activities. You'll need to hit knowledge rank 4, which typically takes around 8-10 meditation spots or equivalent activities, and the optimal path is hitting the northeastern temples first where activities are more densely packed.

Getting your mastery point is the easier part but timing matters here too - side activities marked with exclamation marks give guaranteed points while random encounters scale based on level difference, so prioritize marked content for efficiency. Once you've got your knowledge rank and mastery point head into the katana tree where swift step sits in the middle branch, and you'll want to unlock it right away since it enhances your counter timing windows specifically against flurry attacks which become more common in later areas. The timing for these counters is pretty precise - watch for the enemy's weapon to reach its highest point, then trigger your counter just as they start the downward motion for optimal results.

A good way to practice the new timing is against basic soldiers in the training grounds, where you can safely get used to the counter window without risking much damage if you miss it. Their attack patterns are more predictable and they telegraph their flurries with a distinct shoulder rotation that makes for perfect practice targets.