The approaches laid out seem reasonable, but it's hard not to feel as if the web dev community has moved on to using LESS and SASS as a means of addressing some of the same issues.
Quick example, OOCSS way of making the notion of 'fancifying a thing', is to make a separate class to represent 'fanciness'.
.fancy { color: hotpink; font-style: italic }
.thing { width: 100px; height: 40px }
Whereas in SASS you could do that with a mixin instead:
@mixin fancy { color: hotpink; font-style: italic }
.fancy-thing { width: 100px; height: 40px; @include fancy }
There are advantages of both, and there are clearly variations you could make on the SASS version (i.e. you could make a separate thing mixin too, then mix both into a single fancy-thing class - making the thing concept as reusable as in the CSS version).
Personally I like the level of understanding that doing it the CSS way brings (note this is also an example of the separating 'skin' from 'structure' idea, which I think is very valuable). You could argue that it could lead to class-itis though. Swings and roundabouts.
I personally love using SASS and in fact (as mentioned by philipwalton) find it highly compatible with OOCSS. However, as with any tool, I advocate for thoughtful and critical implementation. I tend to suggest that anytime the final CSS file contains a large amount of repetitive styles or deeply nested selectors it's time to consider refactoring.
More important than any one methodology is consistency and documentation, no one wants to pick up a project with 'genius' abbreviated class names without some example markup!