You might have to sacrifice some skin but no one ever said car stereo installing was painless...no pain...no gain. Plus, the skin will come back.
Seriously, use a cordless butane soldering tool, it works fast and its easier to solder in tight places because it heats up the wire so fast.
2013 F30 328i - Melbourne Red
2011 E90 M3 - Monte Carlo Blue
2004 E46 M3 - Imola red