I messed up on a board design, and used a 0.8mm pitch footprint on a 0.5mm pitch part!!!
So, instead of trying to redo the whole board ($55 or so), I designed a little adapter to go between the two. I had to reflow solder it to the original board. I didn't have any solder paste (I had some, but it had gone off, since it was about 18 months old), so I just used a bit of solder and my flux pen.

Oh NO!!!!!!

The adapter on the left is the back side, which matched the 0.8mm pitch footprint on the board. The one on the right is the top side, and my first (failed) attempt to solder on the adapter. Fortunately, I have three of these boards and only need one, really.

The second (successful!) attempt at reflowing the adapter to the board. I haven't tested all the pins yet, but the 30-40 I have checked are right!!!! Yeah!!!
Gabriel