If designing your own PCB, which you want to mount a pro mini on, there's another trick - make or find a library (or manually place rows of header - but this is error prone) with pins on the board you want to connect to. I usually don't place the 1x6 ftdi header, and just mill out a slot under it, and solder those pins on first).
Then place the pro mini directly on the PCB, over the holes. Put a piece of pin header through on one side. Apply no-clean gel flux to the other side, and then solder each pad, holding the iron against the hole on the pro mini until it wets the corresponding hole on your board - you'll see the solder suddenly suck inwards when this happens.
