I have found that splitting the wires using a thumbnail is not too difficult, and also minimizes the risk of cutting one of the wires.
I have successfully done this with floppy drive cables and ATA/33 cables splitting after every 5th wire or so, and also on ATA/66/100 cables by splitting every 10th wire or so. I then bundled the cable together inside split loom tubing, resulting in a very clean look that minimizes air resistance while maintaining flexibility.
There are lots of methods that people use, but this is the one that I prefer.