For me longtail keywords are purely more finely focused keywords cascaded down from the big money/focus keywords whatever they may be.  So it doesn't matter if they are model related or how any words etc, they are just one way or another the closest thing you can get to a finer granularity exact match the next level from the big volume main keyword.  I think the target is selecting the ones with modest competition and a search volume.

Before using Disavow you will need to make a concerted effort to manually have the links removed.  A good tool to coordinate this would be Rmoov.  I would use Disavow as the last thing, if all else fails.