Hit on the wall last night. Worked on taking the hand slowing to the ball and then pulling up, thru and across. Works very well for me. Also, use it in matches but don't think as much in matches. I don't think "yank" or "pull straight across". I think/visualize smooth approach to the ball with the hand to and will think "pull" at contact. In reality, the rackets speeds up just at or before contact but going slow into contact gives me good control and feel. Also, I think the racket actually is moving up, thru and across simultaneously.
By the way, you can hit the lower outside of the ball and still hit an inside out FH by catching the ball a bit later in your swing path. You can hook an inside out FH with R to L action for a righty, or you can catch it more on the inside or middle of the ball and have a bit of L to R action.
I try not to overthink it. Basically, take my hand slowly and smoothly to contact, pull the hand thru contact. I do not stop the natural rotation of the body which adds an element of thru to the shot.
I am also not too concerned that some pros separate their hands just before the bounce. I train by keeping both hands on the throat till the bounce but I may occassionally seperate a little quicker on a very hard and/or deep shop. Key is thinking wait and take the hand to contact very slowly and smoothly. I actually find I play better against pace if I think patience, smooth and compact to contact.
All in all - Oscar's technique works very well for me.
If I try to separate hands before the contact, and think stretch L arm parallel to baseline as part of the prep. I feel too mechanical and it does not work well.
Take the hand to the ball and pull the hand thru. Use the feel of the hand to direct the shot LtoR and height. Keep it simple. Pull faster for power but always accelerate on the pull even if using moderate rally ball pace.