There is evidence that massaging in non-steroidal anti-inflammatory gels (like Voltaren Emulgel) can benefit inflammatory conditions in tissues immediately under the skin. These gels can be purchased over-the-counter from most pharmacies, without prescription. (Unfortunately, there is little proven benefit for using these gels on deeper structures like the rotator cuff in the shoulder).
For an acute injury, massage gently. For a longer standing problem, massage firmly enough to be uncomfortable, but not so hard as to cause pain. If it is getting painful, move the zone of massage away – nerves in particular 'don't like ice massage. Keep peeling the cup away as needed. Return the ice-block to the freezer when you have finished. You may need to wrap it in gladwrap if you have a frost-free freezer.
Ice massage can be performed as often as comfortable but should be done at least once each evening. If there is swelling, an ice-pack for 10 minutes every waking hour will be of use.
You might like to freeze 2 or 3 cups at any one time, or keep one in the freezer for emergencies.
A small coke bottle filled with water and frozen, or a frozen golf ball can be used as foot massagers for things like plantar fasciitis.
