use water... lol Is that a scratch? Hard to tell in the picture how deep that is. Are you sure wet/color sanding will fix the blemish? IMHO, Chad, let a professional do it. You can make it worse by not knowing the proper procedure. Then there is the buffing. Using a high speed buffer without experience can burn through the clear coat and paint. Again, making matters worse.
On the left are surface scratches, on the right is where my garage door scratched the paint and some of the plastic off. I have been putting a layer of paint on the scratch every day to fill it in.
If you have ever used a clay bar, wet sanding is the same thing. Keep a bucket or a spray bottle with you. Keep the sand paper wet or spray the surface as you go. Very light pressure. Let the grit do the cutting. It will produce a slurry -- milky/muddy paint colored solution assuming you're sanding color. Sanding over/with slurry will cut faster than sanding over/with clear(er) water.
Wet sanding may help that a little, but honestly it needs to be re-painted. Due to how thin factory clear coat is and how much material you remove wet-sanding, you really shouldn't wet sand on an OEM paint job. You can try to wet sand on your repair, but you're likely to burn through the clear on both sides of the scratch before everything is leveled. If nothing else, it will be some good practice before getting that panel repainted.
