These two videos from Steve Sinclair on hand massage in martial arts. He applies dit da jow after punching. I have his VHS somewhere, on introducing Wing Chun, which I watched 10 years ago. What impressed me was that he was the *only* person in his instructional videos to tackle the issue of caring for yourself.
I cannot find his original video, but the way he insists on taking care of your hands how punching a wall bag is a "serious abuse of your joints" really stuck in my mind. It is true. It is self-harm, in a way isn't it.
I bought some dit da jow and apply it to bruises and knuckles in the vigorous way he mentions. He rotates in a small circle and takes off the top layer of skin. The rubbing gets the blood to the damaged area and aids repair. I see here in this video he argues a partner can be more effective, but you can imagine what a solo style of massage looks like.
You can find 'how to' videos on making your own dit da jow and when I researched it, it can get very technical, with many dos / don'ts and very fine attention to detail about herbs etc. I bought mine off a Karate teacher and it seems ok. Smells like Chinese herbs in alcohol :>