Please elaborate! Do you heat just at the crown socket or the whole blade? Front, back, both? Enough to soften the filler or just enough to sort of 'normalize' the cooling? Two of the four I recently built required a touch with the file on the left leg dropout. I had to remove about 0.2-0.3mm to center the wheel after aligning which was annoying.

I have same process as Unterhausen - silver the crown to steerer. I actually leave a bit of extra flux in the sockets when putting the crown on the steerer so I can scoop it out and put more on as I'm going around the crown. I use a #4 which is about the max my tanks will handle. After the crown is on, I cut the headset race, then I flux up the sockets and dropouts and assemble in the jig. Then I do the dropouts and finally the sockets.