My method is really quite close to Michael's
1) Paint tracks with gun metal
2) Dry brush with rust
3) Drybrush lightly with steel
4) Burnish all metal surfaces with pencil lead
5) Complete weathering with a dusting of pastels with the rest of the kit
This method works really well for all steel tracks like that found on the Tiger / Panther. If you are building a vehicle with rubber pads just paint that part of it in black, don't drybrush or burnish this part of the track and move to the dusting of pastels.
Hope this helps.
Happy Modelling and God Bless
Robert