Paraffin wax works really good. You can also use bee wax or even rub a plain candle on the tracks. Apply to the 2 tracks and move the windows up and down a few times to distribute the wax to the window frame. You might have to do this a couple of times before the windows start to move freely.

Another issue with old wood windows is paint build-up. Thick paint can cause sticking problems. It might be a good idea, if you have some carpenter skills, to remove the sashes and sand off any build-up on the edges.