Everyones technique and sequence will no doubt be a bit different based on experience, and what works for them. The path I follow is dictated by my frame fixture. I use the term fixture loosely- and I certainly wouldn't call it a jig (as we've come to know frame jigs). It's a homemade affair, and holds the tubes in alignment after all the mitres are cut. So the first joint to brazed is the seat tube to bb shell. I finish the fillet at this joint because the downtube will hide the front of the seat tube to bb fillet. The I tack the downtube and top tube to complete most of the triangle. I add the head tube last only because that's how my fixure dictates it's use.

I built this "fixture" to hold the tubes in alignment, and match the full size drawing. It has some drawbacks, but works well enough that I haven't been tempted to change it up. After tacking all in the "fixture" I pull it to finish brazing.