I was "lucky" enough to have a problem with the first LC Smith gun I worked on that required assembling it about 7 thousand times. I always started the top and bottom screws just a little. Turned the gun over (on a padded surface)so the weight of the gun was on the top lever pushing it towards the trigger plate, and then use the biggest allen wrench that will go through the plate and into the top lever. Slide the allen over with your finger until the top lever "snaps" into place, VOILA. I did bend the allen a few times, but if you keep your fingers down close to the receiver it should go. I don't like the notched screwdriver idea as it is just something else sharp to drag across your gun if it slips. Jerry Andrews who has seen the inside of a whole lot of these guns told me that is how he does it.
One of the funniest things I read on the LC Smith board was a post about this job where one gentleman commented that it was "OK to cry a little."
CHAZ
