S.B.
D. - as a former Controller/HR Manager, I can tell you right off that the best way to reach employees is through the HR department. And the best way to get any employee to give you time of day is to give them something for free first. Food works amazingly well and can be as simple as cookies. People, in general (and there are always exceptions), feel obligated to at least hear the pitch when they've taken something for free.
What benefit are you trying to sell and in what environment? Let me know & I can give you some tips on what I've seen work with different vendors bringing things in to the employees. PM me....