Gather your tools and remove the contents from the 3M kit. You'll be working with a 500 grit sanding disc, an 800 grit finishing disc, a 3000 grit refining disc, and rubbing compound. Optional items not included in photo are masking/painter's tape (highly recommended) and a small amount of wax (for protection of lens after restoration).

Next, prep your work area. To do this, start by cleaning your headlights (soap and water will suffice, but I like to use Simple Green to remove any bugs and more difficult to remove grime).

Then tape off the area to protect surrounding trim, paint, etc... (two layers of tape is recommended).

Lastly, get your drill ready by attaching the (supplied) Disc Pad Holder and one of the (supplied) 500 grit Gold Sanding Discs. Chuck the holder in the drill as level as possible and center the sanding disc on the holder as best as you can.

In order to get a better lens, we have to make it MUCH worse to start with. Sanding the lens with the 500 grit sanding disc will produce a white, "frosted" look to the lens. This is normal and desired as it removes all the yellowing and haziness from the lens so that we can polish it up to a nice clear lens by the end.

So, grab your prepped drill (with a mounted 500 grit sanding disc) and using light-to-medium pressure, begin sanding the lens with a smooth back-and-forth motion. Do not use too much pressure or let the disc sit in one spot for too long as you will heat the lens and introduce "smearing" which can be difficult to remove. As daunting as this step seems, it's really not bad at all. You just want to gently sand the lens in an even motion until you have removed all of the yellowing and deep scratches from the lens. The image below is the look you are going for. Remember, extra time spent here will make the following steps easier and the final result better.

Frequent cleaning of the disc and lens by wiping them off with a dry cloth will extend the life of the disc. If a disc does become clogged beyond cleaning, swap it for another disc (6 are provided in the kit).

Now that we have the imperfections removed from the lens, we can slowly start cleaning it up. To do this, swap to one of the 800 grit finishing discs (the white discs) and center it as best you can on the holder. Using similar pressure as in step 1, begin sanding the lens with the 800 grit pad in a smooth, even motion.

Make several passes, cleaning the disc and lens frequently with a dry cloth. Continue sanding until you see the coarse scratches from step 1 begin to disappear in exchange for finer scratches from the 800 grit disc. You should still see a frosted lens, but more clarity should be visible.

Now that we're done sanding on the lens, it's time to start finishing it up. Do this by attaching the foam, 3000 grit, refining disc to the drill holder. Using the spray bottle full of water, dampen the foam disc and the lens itself before beginning. This step requires a wet surface, so make sure you spray it down sufficiently.

With an adequately damp surface, begin sanding the lens with the finishing disc as you have in previous steps (light-to-medium pressure in an even motion). You are only supplied one of these foam discs, so take care not to let one of the alignment pins (the 3 "nipples" in the above pictures) or a sharp edge of the lens damage the foam disc. Caring for the disc in this step will allow you to use this kit on many more lenses.

After making several passes, you should begin to notice a white "slurry" buildup on the lens. This is a good sign as it indicates you are reducing the scratches from previous steps. Continue sanding until you have a fair amount of buildup, adding water to the lens/disc as needing to avoid drying out. When done, wipe the lens dry and you should see a lens that appears much clearer, devoid of any scratches.

Finally, the last repair step for the lens....polishing it up. Remove the foam disc and attach the orange compounding pad to the drill holder. Open the (supplied) rubbing compound pack and apply a dime-sized amount of compound to the pad. Before pressing the drill trigger, smear the compound around on the lens in an even fashion (this prevents splatter from cutting the drill on).

Holding the pad flat on the lens, polish the lens until all cloudiness is gone and clarity is much improved. If needed, apply another dime-sized amount of compound and continue polishing. Polish until pleased with final result (repeating step 3 if necessary to remove additional scratches).

You should now have a lens that resembles this...

If you are pleased with the result, grab a small amount of wax (I use Meguiars Quik Wax as it sprays on clear and is easy to apply/buff) and buff into the lens. You should now have a very clear, smooth lens.

Lastly, remove the protective tape and inspect your work. You're all done!