I wonder what the source of the pain is? I have DD and get hand/finger pain, but I don't think it's due to DD but things like excessive piano playing or general misuse of hands when doing things like gardening, DIY, sport, etc. I also have a couple of arthritic finger joints with Heberden's nodes. I can usually distinguish between joint, ligament or tendon related pain and will treat each separately as the case may be.

Try and find out the sources of the pain. Inflammation from misuse, overuse, change habits or try anti-inflammatories or treat as an injury (RICE). For rheumatic or arthritic joints there are OTC remedies that may help. Muscle, ligaments or tendons consult a physio/OT and find a topical such as arnica or Voltarol or capsaicin that might help.

For example I currently am nearly 11 months in with a sore PIP on the second finger and have been treating it with ice, a compression wrap, topical Voltarol and more recently topical FLexiseq. Much to my surprise and disbelief the Flexiseq has helped the most and I am 90% pain free despite a permanent physical change in the appearance of the joint.

More ideas: In your father's case I wonder if a short course of oral steroids would help, in which case that might indicate inflammation from overuse. Also has his blood been tested for rheumatic factors? Has he tried using the other hand for some things. I no longer use a mouse with my dominant hand, it hurts afterwards if I do. I cannot use a trackpad at all on a laptop for an extended period of time. Same thing, it hurts. Some adjustment in practical things is sometimes necessary.

Good luck SB