More often than not when we see these kinds of images some form of digital manipulation has occurred. Of course, all sorts of mechanical and chemical means are also available to achieve similar effects. Partial development of the negatives and/or prints either using brush development or otherwise and/or reduced/no agitation during print development, scratching negatives, using overlays/patterned screens, burning & dodging obviously, bleaching & partial redevelopment, variations with exposure + development (lith, or quasi-lith using regular paper developer), in-camera manipulations with objects held before the lens or intentional light leaks + flare (scratched lens elements) - the list is really virtually endless.
The images in the first post suggest a combination of methods and it's impossible to tell for sure what exactly the maker did. A quick glance at them would lead me to believe that most of the manipulations were in fact made in the printing process and not during negative exposure or development - assuming it's physical darkroom work and not just a photoshop exercise we're looking at. Again, that last option cannot be excluded.
If you want something in particular, I would suggest isolating that aspect and then determining how you can achieve it.