I would seriously reconsider following the steps in that video. To me, it was more like a
highlight reel of what "not to do", than an instruction of "how to do". While the results look good on camera, I can guarantee you that it would not look so good in person.
When doing any touch-up of this nature, the results are not going to be perfect... Major improvement - yes; Perfect - no. With that in mind, my philosophy when doing this type of repair is to keep the repair as small as possible.
The smaller the repair, the less obvious it will be.
The first thing that I would recommend against is the initial sanding of the scratch to smooth the edges. That alone at least
doubled the width of the repair. It also made the paint application more difficult. Instead, I like to use the sharp sides of the scratch as a dam, or barrier, or wall, to help contain the touch-up paint within the confines of the existing defect. And, by doing so you have not increased the size of the defect at all.
Next,
if you fill the defect completely with the color or base coat, and then sand it level with the existing finish, where does the clear go? The clear would have to on top of, and proud of, the existing finish. Instead, I like to apply only enough color to provide hiding, and then finish filling the defect with clear. The only time you should ever apply the color to the level of the existing finish is if you were doing a single-stage (no clear) repair.
Those are the two most obvious discrepancies I see with the process depicted in the video. There's more, but those are the main ones.
I’ve done my fair share of touch-up’s and here’s the process I use…
https://www.autogeekonline.net/foru...ry-chip.html?highlight=discerning+chip+repair
I’d recommend that you take a look at my process and then decide for yourself how you want to proceed. And since this is your first attempt at a repair of this nature, I’d also recommend some practice before promising anything to a customer. A test panel could be your friend here.
Lol. Lol.