LOL susp. air bags

My old co. didnt have air-ride susp. on the trailer the co. I work for now does and while doing a pre trip I noticed I had no air in my trailer suspension. so I drained the air out the rear tank and waited till it filled up and still nothing so I asked another driver for help... he told me to push the trailer brakes in and of course I felt Kinda stupid but they told me the difference between the two..(thanks fellas)....and runnin reefer=long waits