Smooth rotation when dragging

Alright so this script basically rotates an object when dragging across the screen with one finger. I would like to make it more "smooth" thou. Ive been trying alot of diffrent things like lerp and slerp and so on but nothing seems to work, so I thought I might as well post the working code here before I give up. I would greatly appricate if anyone knew to to make the rotation more smooth.

Code (csharp):

1. #pragma strict
2.  
3. private var oldMousePos : float;
4. private var curMousePos : float;
5. var old : float;
6. var touch1 : float;
7. var dual : boolean;
8.  
9. function Update ()
10. {    
11.     if (Input.touchCount == 1)
12.     {
13.         touch1 =Input.GetTouch(0).position.x;
14.    
15.         if (Input.GetTouch(0).phase == TouchPhase.Began  )
16.         {
17.             oldMousePos = (touch1/Screen.width);
18.             old = 0;
19.         }
20.         if(Input.GetTouch(0).phase == TouchPhase.Moved )// This keeps running while finger is held down
21.         {
22.             curMousePos =  (touch1/Screen.width) - oldMousePos;
23.            
24.             if(!dual){
25.             transform.Rotate(0,((curMousePos-old)*200) ,0);
26.             }
27.            
28.             else{dual = false;}
29.             old = curMousePos;
30.         }
31.     }
32.     if(Input.touchCount == 2 )
33.     {
34.         dual = true;
35.     }
36. }