you just need to tout yourself to more than this one firm you've been helpin out.
i'd say you need 3 x firms to sub to if you wanna keep goin, although when one's quiet its usual that they're all quiet...and when its quiet you're goin to keep your own drivers happy 1st, subbies 2nd...and you need to be flexible and be ready to go asap to keep gettin work from them.
The 2nd half of August was pretty quiet, but you should be findin it ok from now up to xmas i'd have thought.
Networking is what its all about....tell people you're available on what days and when, your mileage rate...when you move tell em where you're goin....they're more likely to give you a job goin in similar direction if they know where you're goin...and ring ahead to companies in the area you're droppin off at to get return loads