I found a way to speedup the ceiling tiles drawing.
1) draw large areas (surrounded by hallways)
2)create walls with double lines as polygons
3) add other polygons going through the ceilings (columns etc..) with solid color, this makes viewing and later selecting easier.
4) select all areas and subtract #2 and #3 from #1
You have now the inside of every space
If you need install light tracks, offset this boundary by 2 ' or so for wall wash
etc...
I am happy with that but there may be the option of filling between walls also to save even more time... Just thought about it!
Tell me what works best for you
Best to all