My learned defensive shooting technique is whatever works for me.
I do not ever try to count expended rounds.
Because I know that "counting" will likely never work when the S.H.T.F.
The slide locking back should trigger an immediate auto response to reload.
I am ALWAYS extra careful about shot placement since I often carry a European SIG P220 w/ the mag release on the butt.
That requires lots more manual dexterity to effect a necessary lightning fast reload.
Like anything else that we humans attempt...it can be done swiftly with repetition, practice, & good motor/muscle memory.
Naturally, common sense dictates that it would be ideal to have the "business" already ended before any panic reload is necessary.
Since all of my primary carry guns are single stack .45 & NOT double stack "other calibers" ~ I personally would always "drop" a partially expended magazine (after there were "Shots Fired") in favor of a full one should there happen to be be a lull in the defensive shooting scenario.
That is just me...I don't expect everyone to agree with me or to follow my way of thinking.