Farming run in Laby/Zokor

Hi guys I've ran out of GG and I need to go on a farming run. Problem is, I don't really know how to go on about it. All I'm doing right now is clearing the first hallway and if my first intersection doesn't have a farming door , I'll retreat. However I've done this about 8 times and even if my first intersection has a farming door my next few intersection will not have one , resulting in me having a lil over 20 farming clues when I reach Zokor. Is it a must to use cubes to have a successful farming run and must I use GG all the way ?