And for the vinyl tracks,
Painting:
wash them first in isopropyl or denatured alcohol and let them dry on some paper towels.
I primer/base coat mine with Rustoleum Flat Black enamel. Shake the can for at least 1 minute after hearing the ball inside start to rattle.
Then flow in pastel pigment / acrylic sloppy washes of red browns and then to dirt browns until the look is where I like it.
Lightly dry brush a gun metal color where the "steel" parts contact the wheels and the ground.
Use the technique described in the I-Sheets for connecting the ends. Probably the hot screw driver method.
Installation:
The drive sprockets and idler wheels shouldn't have been glued or installed onto the model yet.
Wrap the loop of track around the idler wheel and the drive sprocket in the approx. appropriate locations, then install onto the model.
The sag can be achieved by gluing to the tops of the road wheels and around parts of the drive sprockets after installed onto model. CA glue works for this.