I believe the swing goes bad before it starts for most kids. The preswing is more coachable than the swing itself .

I read this cue and like it.

" Both thumbsnails up and almost facing pitcher during the load."

supports top palm faces pitcher during load

Supports bottom hand under top

Supports lead elbow down and rear up

Then...

Maintain bent lead elbow through early rotation/ first move or mainatain box through early rotation or elbows change relative positions but stay bent during early rotation