From you description it sounds like ypu're trying to balance the rudder while it's hanging vertical from one hinge point and thats not going to give you a balanced rudder...
Keep in mind that the balance of a control surface (either mechanical balance or aerodynamic balance) centers around it's entire pivot point (fulcrm) and in this case all 3 hinges make up that point. Hanging a surface from only one hinge would allow the other 2 to either lead or lag and create a false fulcrm.
Simple and quick way to balance a surface;
With strap hinges (Pitts, Eagle, etc.) block up the control surface on a long FLAT LEVEL table using 2" aluminum angle under each hinge point. You basically are making a teeter-totter out of the surface.
With pin type hinges build a "gallows" out of 2x4 long enough to hang the control surface under it... _/---------\_ insert the pins into each hinge and hang the surface using safety wire (you can use anything to hang it but take into account the strength of the wire, weight of the part and the fact that Murphy hangs around in workshops a lot...) through the hinge pins hang the surface LEVEL..
Balance to taste!
This is just the way I do it.