I run the wires the opposite way. I've seen guys crash and the guy who came in from the rear got something tangled in the wires and one of the leads was unplugged. I'd rather run them inward and kill the possibility of that EVER happening.

As for Flux, it is an excellent additive for certain applications. So long as it's not used in excess it actually assists soldering by better transmitting heat throughout everything with solder that is in contact with the tip of the iron. The shinier finished leads are usually achieved with Flux. In fact, if you turn over some ESC's and look at the solder points, you can usually see flux residue on and/or around them. The hotter your iron gets, the less flux you'll need. I use a little flux but the way I do it is to scoop up a tiny bit with the end of my solder and once the lead is up to temp, I then slide the solder onto the wire and the flux makes the tinning process almost instant and I am able to use less solder as a result.