It's been a while but we're slowly getting back into it.
A few days ago I took an old sock (tucked into the waistband of my shorts to help with scenting) and Tali's giant rope bone to the footy oval and we did a couple of easy tracks to see if he remembered how to do it. He had exactly no trouble remembering how to do it, and the fact it was a black and grey sock on green grass probably didn't hurt. He can at least use both his eyes and nose at the same time and even managed to find it when I draped it over the fence above his head.