What type of arrester and where did you install it? To work, the thing needs to be as close as possible to the offending valve. Some valves shut off faster than others. You might consider a Korky Quiet-Fill valve or a Fluidmaster (assuming either of these would fit - they do on most toilets). Draining the water will have little, or short term, if at all effect on a water hammer situation.
Air columns don't work, or if they do, don't work for long. It is almost impossible to drain them, too. Think finger over the end of a straw...that's what you've got there. An engineered version uses a piston or a bladder so the air can't be absorbed into the water.