For Fastbond 49, the best maintenance method is to keep the system full of adhesive and closed. If you can avoid letting air get entrapped anywhere in the lines or spray gun that would be best. Stainless steel and plastic parts are the only materials to handle 49. Other metals will cause coagulation.
If you need to clean the lines, acetone or our 3M™ Aerosol Adhesive Remover work best on dried 49.