B25,
As a coach you must create a hitting system at your school that works. You find the absolutes and go with them.
I believe that Englishbey's
Posture, connect, rotate is efficient. It can be the similar to nostride, bat in 45 slot, drop and tilt...although they would say not exactly but as far as player understanding pretty close.
The connect portion ...I take to mean the bottom hand lead shoulder connects to the turn quickly helps get the barrel out in the zone with force.
To best do that...IMO...the details.....
the lead elbow is down close to the body ( maybe what you mean with the towel drill) as the stride or shift begins.
If the top hand is pronated ( palm over/ bat cocked) then the rear elbow elevates and internally rotates to get in the proper position inside the target line.
then...
Rear elbow action is up(top palm angles down) then elbow internally rotates then slots/ external rotation/ top palm up.
A slight plane change from at least splitting helmet to 45 launch aids this rear elbow action and makes loading work well.
It insures the fact that the hands will come out knob to oppo box and the barrel will get out there from flail.
The lead elbow starts close to pect then as the bat flattens it goes into the plane of the pitch.