Hi Gal,
We have many brake examples in Simscape Driveline. I think the best way to model your system would be to take a shipping example and replace the hydraulic system with components from the gas library.
Try looking at example >> sdl_braking_caliper_disk_brake
See online documentation here: Fixed Caliper Disk Brake
You can replace the hydraulic blocks with blocks from the Gas Elements Library. Below is a screenshot of one subsystem that shows the integration of the hydraulic and mechanical domains. Replacing the blocks in the blue field with gas libary blocks would be a good step.
--Steve