Running it on just 22 should be pretty effective on it's own. Large scale port scanning is semi-difficult, as you'll get banned really fast, even if you're just scanning an uncommon port. To pull it off, you'll either need your host to be okay with the abuse complaints (that are usually automated) or have a botnet/proxy list.
However even then there's 65535 different ports (not to mention almost 4.3 billion ipv4 addresses), and you'll likely can firewalled off pretty fast. So instead of scanning 65535 ports, scanning just 22 usually works anyway, as few people change their ssh ports (and those that do are more likely to have other security measures in place)
However even then there's 65535 different ports (not to mention almost 4.3 billion ipv4 addresses), and you'll likely can firewalled off pretty fast. So instead of scanning 65535 ports, scanning just 22 usually works anyway, as few people change their ssh ports (and those that do are more likely to have other security measures in place)