Sir,
Just for your information here, it's BRAKES not BREAKS. And, this issue may or may not be a real problem. You see, you're using AIR for the brake application, not hydraulic fluid. I'm pretty sure you know that but, just reminding you of it. Air, IS compressable but, HYDRAULIC FLUID is not. So, when hydraulic brakes are adjusted correctly and, there is no air in the system, you will have a fairly HARD pedal when the brakes are applied.
But, since you're dealing with an air system, and by virtue of how the entire system works, you are compressing air, to make things work, in the brake assemblies. You don't say how many miles you presently have on your coach or, if this is a somewhat recent issue or, have you thought that this was an issue since purchase?
And, upon extra hard application, is your coach stopping in a somewhat normal distance, based on speed at the beginning of the application?
As for "easy way of adjustment", well, adjusting air brakes on a diesel pusher is not for the un-informed. It's not a hard job, but, is somewhat technical. After all, you're messing with BRAKES here so, the job must be done correctly and by someone who's educated in the field.
And, about 99.999% of the D/P coaches out there are equipped with what's called "Slack Adjusters". Those are attached to each brake can, close to each set of brakes. They are mechanisms that are designed to see the total movement in each brake assembly and, upon fairly hard brake applications, will automatically adjust any abnormal slack in the system, to eliminate it so that brake shoes, travel the absolute minimum distance to the drums and or, pads to discs. Hope this has helped some.
Scott