A couple recommendations for you. First, Scratch X is an abrasive polish, or polish with "cut" so it should work fine on your scratch. Idealy to use this product you would want a polisher with the appropriate cutting pads. A great way to use it if a buffer is not available, is a foam or wool polishing or applicator pad. pads are organized by color and material according to how much they will cut the clear coat. Start with the least aggresive, and work your way up till the scratch is gone. Another thing to note is, after polishing a vehicle with any abrasive polish, your paint system is fully exposed to the enviromentall elements. A proper wax application of the area polished is ablsolutely necessary!
There are other ways/chemicals to acheive a higher cut or seal if this doesnt take out the scratch. Or if you are not happy with the results.
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