Having trouble conceptualizing what I'm actually supposed to be doing once I know my SID (shiny starter farming Fire Red)

Hi all,

So I saved my game in front of Charmander and then proceeded to play through to Celadon without saving so I could mail glitch my SID and then reset the game.

So now I'm at the beginning again and know my SID for sure, but I'm having trouble understanding exactly what I'm supposed to be doing. For most of Blisey's guide he is trying to find his SID, then all of a sudden he hits the shiny. I think I'm just lacking some basic understanding on what is being done here.

Am I supposed to put my SID into TenLines and then just pick whichever shiny seed I want to attempt, and then it's just a timing game? Or do I still need to do more "calibration?"