Best man to man defense drill I have ever used is making your defenders guarding players without the ball to make them have their hands clasped behind their backs.
This forces them to move their feet and not to reach. Because if they reach, “The officials will teach”.
When the man they are guarding receives the ball then they may unclasp their hands and guard them with their hands. Make sure that they use their left arm and hand to guard a right handed shooter asnd vice versa for guarding a left handed shooter.
In the post as soon as the entry pass is on the way to the post player then the defender may unclasp his/her hands from behind his/her back and use their arms and hands to play defense.
HOWEVER AS SOON AS THE PLAYER THEY ARE GUARDING WITH THE BALL, PASSES THE BALL TO A TEAMMATE, THEN THE DEFENDER NOW MUST CLASP THEIR HANDS BEHIND THEIR BACK.
Coach, make sure you are on the endline behind the defense and if you catch a player not keeping their hands behind their backs when they are guarding a player without the ball and not using their hands when guarding a player with the ball….blow your whistle and have that player run a lap and then sit until another player breaks this rule. Or if you have other players sitting out then they have to wait until it s their turn.
This is an excellent drill to force your players to move their feet and to stay in the correct defensive stance.
I have on occassion even used this drill in an actual game.