As promised (a year ago or more) attached are a couple of photos of my parking lot track. It is made from 1/2" MDF and I used your routing guides to make the slot. The track is painted with two rolled coats of grey flat latex (as per you video) and the lines are made from correction tape used with type-writers (is that still a word?). The intesting thing about the tape is that the car tires selectively remove it from the racing line. I use "Trakmate" timing with the light in a home made gantry.
The track has been running for just over a year, and I've probably put 2000+ laps on it. I have a variable power supply that I have currently set at 10 volts so I can get a comparison between various cars. Right now, my fastest car is an "illegal" Ninco mini (14 grms of lead, slot-it yellow crown gear, zero grip front tires, S1 rear tires, however the rear wheels stick out past the body) with a best time of 8.253 sec. For comparison, my Slot-it Audi's best time is 8.497 sec and my slowest car is a Scaley Maseratti at 11.037 sec .
I find it quite interesting to play with a single car to see how it's time can improve. It seems the longer I run it, the cleaner the track becomes allowing the times to come down.
I've bought some 3/8" MDF and have been playing with a new layout for a 3 lane track which I will build sometime this year.