Removing the CellBracket is handled by the option setting (within the Cell expression)

ShowCellBracket->False

However this still leaves some vertical space before and after the cell, and it seems one cannot get rid of it by choosing the vertical spacing options for the cell in question (coloring it gray so you can see where it is). Execute this to see:

CreateDocument[
 {TextCell["This is some text", "Text"],
  TextCell["This is some text", "Text", ShowCellBracket -> False, 
   CellOpen -> False, Background -> GrayLevel[.7], 
   CellElementSpacings -> {"ClosedCellHeight" -> 0}],
  TextCell["This is some text", "Text"]}]

The issue probably is not the closed cell itself here. It is that the cell before it has an default option to place space between it and the next cell, and the cell after the closed cell has a default option to place space before it and the cell above it.

As for finding closed cells that have no cell bracket, if they are input cells, one could select all input cells and then use the menu optoin to make all cells open. Alternatively, a more sophisticated approach is to tag cells and programmatically find cells with the specified tags and reset their options to make them open. A bunch of stuff about tagging can be found here:

http://library.wolfram.com/infocenter/Conferences/7246/