Any suggestions on where to find the unmarked single track appreciated.
tl;dr; get a garmin or a tour as this probably won't make much sense and will be pretty much impossible to follow.
If you follow red from the school lot, you will eventually get to the intersection where you can go straight to stay on red, or make a right on yellow. Stay straight on red there and descend a bit, and then make a sharp right to a singletrack climb at the bottom. If you get to the white trail intersection by the circle then you just missed it. You'll likely blow by it the first time, so just turn around and then it will be a left. Climb and descend that, then stay left/straight where it dumps you out. Making a right there would put you onto yellow (don't do that).
This trail will dump you back out on red eventually. Make a left onto red, and then a quick right onto an unmarked trail. Shortly after this the trail splits and you can go left over a rock or right. Right is more fun in this direction. This dumps you out on the yellow fireroad eventually near where it intersects with red. If you made a left here, you could climb up the fireroad a bit, and make a left which might be hard to see back into the singletrack to finish this loop and end up where you started it. Instead of doing that short loop though, go kind of straight across the fireroad and take yellow for a short bit. In a few hundred yards, make a right onto some unmarked singletrack that has a shorty rocky descent.
Follow this trail, and it eventually dumps you back near yellow. Making a left where it dumps you out puts you on yellow (don't do that). Instead, make a right onto the doubletrack, and then a quick left onto the singletrack. Follow this around for a bit, and keep your eye out for a left turn down some switchbacks. There is a small pile of rocks there. If you miss this turn, it puts you back on the doubletrack heading toward yellow where you came out before. The switchback descent crosses some water at the bottom (after crossing the red trail which you could take out to reservoir dr), and then you make a left to do a switchback climb. It crosses an old fall line trail a few times. At the top it crosses yellow, and you want to go straight over some small logs that look like they are blocking off the trail (so don't take yellow in either direction).
When you come out to an area with a small pond, ride the little skinny spot to the right of the pond where there are some rocks put down. Then you climb up the rest of the way almost to the top. You eventually dump out on yellow again, make a right and then you are at the very top. Go past the lookout and stay right of the yellow fireroad. Look for a switchback descent. If you miss it, you could go down yellow a bit and make a left, as the descent crosses yellow not too far down. You'll eventually end up on yellow. From here I would make a left on yellow, and follow that back to red. Left on red and back to the car.
There's more here, but this will give you a good overview if you can follow it. Odds of that without a tour or Garmin are slim to nil though.