After the comments I thought I ought to say I really am not smart with this smudging malarky. I use Photoshop LE and it has a little smudge button you click and move the mouse curser while holding down the left click on the bit you want to smudge.
I've had a look on paint, but I can't see a smudge button, but I guess you could use the eraser and d the same thing.
See not clever at all!!!