I bought a Clark adjustable mainspring (from Gil Hebard) and installed that in my Security Six. The mainspring guiderod was threaded and a nut installed on the end. By moving the nut, you adjusted the weight.
On the trigger, I slowly polished the sear, hammer and trigger on a hard arkansas. I also lightly polished the pawl (hand) and the cylinder stop. The mainspring guiderod (or is it called the hammer strut) which engages the hammer (the round part) was also polished. My polishing method was to lay the piece on the arkansas, keep it level and moving it slowly across the well oiled surface of the stone. This was done several times and the part refitted. A lot of testing (requiring reassembly) was required, and then it was disassembled and polished some more. The whole process was repeated until I was happy (and safety of the working mechanism wasn't compromised).
Vigilantibus et non dormientibus jura subveniunt