Im trying to preserve a longboard?

you really should varnish it if you want to ride it for safety reasons, you don't want it to fall apart. clean it real good with soap and water, nothing too harsh. then to preserve the 'rustic' look be sure and select a clear satin varnish, i say satin so it won't look too shiny, like min-wax or varathane, the top two best sellers. hope this helps