I went to Bunnings & bought a electrical wire plastic thingy that was about 1.5cm wide and about 0.5cm deep and was about 1.5m long for about $7 if I remember right. It has double sided tape on one side and I cut the length I needed to reach from the top gutter to the bonnet (I mounted one on each side of the A pillars next to the windscreen). I then ran the cable from the roof rack, through the plastic thingy, through the gap in the panels and through the firewall to my switch.
I can take a photo if you like, but I found this way I don't have to drill holes of risk squashing the wires. Plus I have enough room to pass about 5 thickish wires each side (not that I need to cause I prefer LED lights).