I have a deep scratch on the side of my truck that has been coated with touch up paint to fill in the scratch. My question is what is the best way to smooth out the touch up after it has dried?

 

A close-up picture of the repair would be helpful. If it is simply a matter of blending the surface I would guess a polishing compound could work. Anything further depends on what you have to smooth out. A picture would help.

 

Langka is supposed to work pretty good on scratches. Dr Color Chip is another although I think Langka is more along the lines of what you want.

 

Stick with a polishing compound. Don't use the fine grit sandpaper. I tried to wet sand it with a kit you can buy at the auto parts store and made it worse. I learned the hard way on that one. Doh!