What would be the proper stone or file to use for making modifications to the profile of a Ruger 77 MarkII trigger and sear? If the ideal is something specialized, is there a common substitute more readily available for working the flat surface?
"...think of this advice..." I'd be leery of any internet page that does say who the guy is and what experience he has. You may want to considered changing the springs only, first. That'll drop the trigger pull. Wolff Springs has a 'rifle tune up' pack for $10US. Comes with a striker and sear spring. Add the W's.
.gunsprings.com/RifleShotgun/Ruger_RsNF.html#77
If you do opt to do anything else, don't use any files. Stones only. All you need to do is polish the mating surfaces, not remove any metal.