BTW Huey my sons personal batting practice pitcher (me also) sucks...so I sit on a bucket behind an L and do soft toss for them from 15' or so feet away. they both hit between 3 and 6 days a week with me for 8 months a year. it depends on the season, winter they are just with lessons and teams it is my offseason! March-April we hit close to 6 days a week, May-August there is so much being played and practiced we cut it back to 3 or so days and often only 50 swings, fall it tends to kick up a bit as the schedule is lighter. November is off month and December is light.
Overhand BP may be best but I don't believe it is mandatory. I think muscle memory and quality reps are the key.