No special soldering except lots of it and little bitty fiddly. IMHO it's not worth the trivial cost savings to DIY, especially if you include the value of your time in the cost of DIY.
Steve, I´ve plenty of time so that´s not a issue right now.
Richard, in a recent shotting day with a RED camera, they used a large HD picture playback system that hadn´t audio input, so, I needed a breakaway cable to let the director hear the playback of the recorded material, I figured out with a headphone extender, but I was lucky because we were shotting in a studio, but that could be a messy thing in outdoors or larger space.
As sad it will sound, there´s no Comtek systems to rent here in Argentine, and if you manage to get one, it will not be at good cost, that´s for sure!