How to best reduce number of workers in your facility?

Carry out a current state and desired future state VSM (Value stream map).  When you do this, you will automatically see bottleneck areas in your process.  Work on eliminating them using Lean tools or TPS methodology.  

You can also draw a "tree" diagram which maps every single item of your process.  Every movement, every action should be mapped.  When you study this, you will see many things which you unnecessarily do, i.e. which do not add any value to the product.

Work on eliminating these items.  It may be as simple as unnecessary paperwork.  When you do this, numbers will automatically come down.