This is my biggest problem. I actually just built my first coil for my Subtank a few days ago. Mostly out of curiosity not necessity and the hardest part was trying to get my hands to stop shaking long enough to get the darn screws back onto the base while holding the coil in place.
I just loosen the screws and the legs of the coil slide right next to it and then tighten them back up a bit, adjust the position of the coil and then tighten them all the way up. I hate having to place tiny screws in tiny holes with the size of the mitts on the end of my arms. But when I need to (like mounting a new mother board for my computer into the case) then I use a very fine needle nose plier to hold the screw head and twist.
Of course for me I have to mount the coil under a desk lamp magnifying lens as even with reading glasses it's not enough for me to see that fine of work.
I use the Realspace clamp on magnifier from Office Depot:
http://www.officedepot.com/catalog/...ge Zone||&cmPredSearchABTestAttr31=magnifying
I had to get it when I thought I was going blind, my sight kept getting worse and worse until I could only see out of the corner of my eyes, then finally went to a eye doctor (I didn't go prior since I just thought this was it, I was going blind and nobody could help) and it turned out to only be cataracts in both eyes, so they fixed it and I can mostly see now but still need the magnifying lens to see really small stuff like the coils legs.