Rao, your search for BTDT info on this will likely be fruitless. I've been looking for almost a year and half, because I want to do the same on my 2000 Legacy GT. Eventually, I will get around to figuring it out, but I can't even find a decent shop manual, yet.
That said, the reason DRLs are a bad idea is two-fold. First, they don't scale at all. While one lit car may stand out, when you are faced with a dozen, they just blend.
Second, and more importantly, human eyes don't see light; we see edges and movement, for the most part. Lights which hamper this, reduce our visual acuity. Ask the US Army why they use bright lights to camoflage tanks in the desert. When the sun is out, your lights should be <strong>off</strong>.
The problem of drivers too ignorant to remember to turn on their lights is best solved through education and enforcement, not inappropriate application of technology.