Great article by John and good practical advise per usual.
Would add,on the target subject. I carry those flourescent orange stick-on circles that come in various sizes from 1/2" to 6",and vary them according to scope power, reticle and distance. For example, I use the 1" size against a black background with a 4X scope at 100 yards; a 3" size with a 4X at 200-300 yards,etc.
The reticle contrasts nicely against the bright orange, yet forces you to "hold small" with the 4X,which results in some pretty tight groups.
I have found the 6" dot does well with a 6X scope clear to 600 yards for me.So I use it at 400-500-and 600 yards.
It is wise not to have the dot too big for the power and reticle because you will then start floating around the dot,your aiming point not being as precise,which will affect group size.
These dots also help you see parallax very easily when it exists at a distance as the movement of that orange dot becomes very apparent,forcing you to move your eyeball to the center of the scope for a consistent sight picture.
If you can't find the diamond targets, these dots are a good substitute.
I am not surprised at the smallish groups with the 4X scope.
