To remove pins from boards, the best and fastest manual way to do so is with a sharp wood chisel.
Position the blade at the base of the pins with a slight angle (to the arrangement of the pins, not the board) and tap it with small hammer.
Leave the soldered 1-2mm left over on the board, it's just not your time and health breading this cr*p from desoldring.
Also, any solder on the pins will produce a handful of problems were you decide to chemically process them.
Been there done that...
Just to give you a perspective,
Personally, i would never (commercially and non commercially) process computer pins chemically/electrochemically (depalting), it's just not worth it.
The only exeption in case of pins are those of CPU's, where the ratio of plated surface to mass relatively high.
When you have several pounds of clean pins and you complete your furnace, we can talk business