I recently started a new kit from Downtown Deco.  It is a hydrocal (plaster) kit of a back alley.  Basically it is a series of five buildings that are only a couple of inches deep, designed to be placed against a backdrop.  I was given this kit, unfortunately a couple of pieces were broken and the box cover was missing.  With the cover missing I had to look online for pictures to figure out how to put together the major portions of the kit.  The instructions were pretty good, but were missing an exploded diagram to identify each of the pieces.

I glued the broken parts back together by using white glue.  This worked pretty well, however for the next model I intend to try 5 min epoxy.  I then glued the walls together again using white glue.  I found that this was a little bit brittle, but does an OK job of holding the fairly large pieces together.  I came back the next day and filled the gaps between the individual pieces with putty.  Sculpting tools assisted in filling the gaps to make them look less like a gap and more like a damaged area of the building.