It's dark when I go to work. It's dark when I get home.
I bought an LED (lighted) collar (dirt cheap on line). There is a street light on the property.
I try to work near that light and with the collar, I can keep track of an otherwise impossible to see dog. We obviously don't make 200 yard retrieves but I can put his energy into a little practice.
Any other tricks for training in the dark?