Slip-It sliding compound (silicone free version) is what we’ve been utilizing most recently with excellent results. It’s effectively a synthetic paste wax that doesn’t seem to attract dust and lasts a fair amount of time. Apply to both the linear slides and the aluminum rails themselves with a rag and wipe off any significant excess with Alternatives are normal paste wax like Johnson’s or Minwax Spray-on dry film lubricants like white lithium, molybdenum disulfide, graphite, or other lubricants like bearing grease really aren’t what you should use. You can, it isn’t going to hurt anything material-wise, but it won’t be effective.