My technique for descending via is to put top altitudes for the STAR in the FMS, bottom for the next fix in the altitude selector, and keep the VS set to a rate higher than what the FMS requires. Keeps you in the gap without having to do anything real thinking. Adjust VS as necessary on the way down to help with slowing and to avoid leveling off at each fix. No more ASAPs for busting altitudes and speeds because you didn’t know what the airplane was doing.