I don't have experience with it, but some version of "that stuff" has been around since my husband and I were paying attention to things like that (decades ago). Exactly whose approach is what approach can be a little different, but I really think a person needs to have a certain type of personality to do some of those things; and I think the region may make a difference. The real estate market in, say, Detroit is a whole lot different than the real estate market in Boston, or in a lot of the suburbs not far from it.
Also, I once saw "a thing" on, I think, Nightline about a young guy who did really well following one or more of "those program", but then he ended up in some horrendous, legal/financial disaster.
My guess is that SOME of those techniques/approaches can/do work for SOME people, but I think people need to really be careful about understanding their own nature, their own ability to invest the kind of/amount of effort needed, the realities/nature of the real-estate market they'd be looking at, etc. etc.
Obviously, since it's not something I'd do I can't offer more than my own reasons for not doing it (or at least that I have my own reasons for not doing it). I just know that some of the stuff they tell people to do is stuff I'm not about to do for one reason or another.