I know a HUGE gold farmer who just straight trades to his mules.
His bots gets banned, but his mule(s) never get banned, as long as he doesn't bot on them.
Other than that, to be SUPER safe, make the mule on a different IP and only ever log into it on that IP (separate IP than your botters) and stake it over, or just trade some junk items back for the GP.
Jagex mostly bans botters more than gold farmers anyways.