Great work and progress thanks for the detailed shots and love your work! That car automation system is great, look forward to seeing more people incorporate them into their layouts.
Slightly different but I have a slot car track in the center of part of my layout and had used sandpaper like material on the hills for cars loosing traction. However I have found that it tends to wear down the car tires very fast. I had a big truck that was slipping a lot and one day recalled a pile of worn O Gauge train traction tires that had come off of locomotives. I wrapped these around the drive tires and it worked great! While I doubt that you will find a small enough O Gauge rubber tire that might slip over your car tires perhaps you might try some Urethane rubber rings or cast your own! They stick very well. Another alternative is using HO Traction compound like "Bullfrog snot" http://www.bullfrogsnot.com/
