One of the opportunities challenges of assembling my airplane has been starting nuts in hard impossible to reach places. Two of the nuts are in a position that is even difficult to reach with needle nose pliers. I remembered seeing a flat nut starter tool years ago which would be perfect for these nuts so I made one from a couple scraps of aluminum and two rivets.
Here is a picture of the tool, holding a nut. (Click this picture, or any other, to see a larger version.)
The top plate is solid. The bottom plate is slotted so that the bolt can reach into the nut.
Once the bolt starts threading into the nut, you simply pull the nut starter tool off the nut, replace it with an open-end wrench, and tighten things as you normally would.
Here is the nut starter tool in position on one of the impossible-to-reach nuts.
I do not remember where I first saw one of these but I could not find it in a store. It only took a few minutes to make, though. Hopefully this will save you some time and frustration some day.