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I've tried to quote the things from that thread but can't make it pretty.

Two comments slightly different from your recommend:
Shot should be released on a 2/3rds exhale. This is the point when...

Alternatively shitcan all that and get a 12ga and a fast bike :D

Get and learn to use a sling, this halves most people's groups.
Drill the fundamentals - hold, breathing, trigger pull, follow through. Consistency is key. Get a stupid-high magnification scope and...