What are the most effective methods for cleaning and greasing gravel bike cable ends to ensure optimal performance and longevity, and how often should this maintenance be performed to prevent corrosion and cable fray? Are there any specific cleaning solutions or greases that are recommended for gravel bikes, and what are the benefits of using compressed air versus a rag and solvent to clean the cable ends? Additionally, how does the type of cable material (e.g. stainless steel, galvanized steel, or lined cables) impact the cleaning and greasing process, and are there any differences in maintenance recommendations for hydraulic versus mechanical brake cables? What are the signs of worn-out or corroded cable ends, and at what point should they be replaced rather than cleaned and greased? Are there any best practices for storing gravel bikes during the off-season to minimize cable corrosion and damage?