I had a similar problem. My cover just didn't make it easy to feel the volume switch and since the iPad and iPhone can be held in any position it wasn't consistent to find the hidden volume switch under the cover.
Yes you can do it from the Settings, General, Sounds menus but it is easier and faster to rip off the cover and find the actual switch.
If the device is not locked, simply double-click the home button and then swipe to the left and the volume control will appear. If it's locked, just double-click the home button
This seems to be the fastest and easiest way to consistently access your volume control.