A good grease

Any recommendations for a good grease for window mechanism runners? My dear old BMW E34 suffers from slow windows in part due to 30 year old grease. I could do with something that will give a nice smooth action, without frequent regreasing (I don't fancy taking the door cards off every 5 minutes) and I don't want a grease that will pick up crap and gum up.

Advice much appreciated!