Place your finger in the middle of the back of your partner and try and keep it there.
The partner then walks around changing direction, stopping, starting and side-stepping etc.
After about 30 seconds change who is leading. If there is an odd number of players there will need to be one group working as a 3. They just form a 3 in a line and the front person leads.
The person following should have bent knees and be in a ready position so as to be able to change direction at any time.
New hitters rarely miss because of their arm. They miss because of their feet. Build a reliable approach, then time it with your setter.
When your hitter gets stuffed, five teammates standing and watching is how you lose the point. Good attack coverage turns a blocked ball into a second swing.
Coaches spend hours correcting arms in serve receive when the real fault is almost always the feet. Fix the movement and the platform fixes itself.