One of the assumptions of a LUT is that they assume that there is good footage going into the LUT in the first place. It's the ol' GIGO problem (garbage in, garbage out). What I do is pretty much what they show in the video. I use DaVinci Resolve, so I have a corrections node before my LUT node. First I look at what I'm getting from the LUT on the scopes, without any corrections. If they look like they are in range, and it looks good, then I stop...usually that's not the case haha. So, if I am blowing out the highlights or crushing blacks, I'll adjust that in the correction node until it looks good in the scopes. The LUT will expand your dynamic range, so you don't really want to go correcting before evaluating what it looks like in the scope first. Sometimes the LUT won't be able to get the footage where you want it, and that's usually due to poorly exposed source footage, which is the point of the correction node.
Hope that makes sense. There's a lot to learn in color grading, it'll take a while to get comfortable, but the results are really worth it IMO.