This is NOT the correct way or technique to remove scratches. As much as I enjoy watching the videos Dave produces, he is not corect with that particular one. He did not allow for the sandpaper to soak for 15-20 minutes prior to using it for defect removal, nor did he follow proper procedure (i.e. sand for 8-10 strokes and check, repeat, check, repeat, check, etc, until the defect is gone). On top of that, you NEED a high-speed rotary buffer with the PROPER compound to fully remove the wetsanding scratches, or they will never be truly removed - only masked. In addition, the products he used were not correct or suited for the particular job he was undertaking.
Perhaps Dave is better-suited with continuing to make videos about repairing beaters, jumping Sky Hill, and preventing the abuse of alcohol (as he always says) - but for God sake, paint correction needs to be left to people that know what they are doing so that average person does not damage their paint by accident.