An elderly friend of mine has arthritis in her hands so bad that she can no longer put hair spray on. Her fingers are so weak and twisted that she can't push the nozzle down. In the paint section at Walmart, I ran across a pistol grip that is used for spray paint. It is so much easier than that little push nozzle! It just slips onto the can of paint.
This is a page about opening jars with arthritic hands. Arthritis can make simple tasks difficult and even painful.