Blow them out with compressed air. Lube if needed with a "dry" silicon spray. No oily residues to collect stuff. This is very good for window tracks as well.
Amazon.com: 3M 08897 Silicone Lubricant (Dry Type) - 8.5 oz.: Automotive (https://amazon.com/gp/product/B000PJED72/ref=oh_aui_search_detailpage?ie=UTF8&psc=1)