Training the fingers of your right hand to be flexible is important. It especially helps in certain kinds of string crossings (which means getting from one string to another). If you don't already have a good bowhold, you will develop one by doing these exercises. And if you can't do these exercises after a few weeks, then your bowhold (the placement of your fingers and thumb on the bow) probably needs to be changed.
Here is an updated link where you can buy some of Martha Gerschefski's excellent books. (I believe more will be added as they become engraved) Martha Gerschefski's Books | Edizioni Migliori (square.site)
Below is a video on increasing the sensitivity of your bow fingers (with a mitten exercise)
The next video is short and shows another finger flexing exercise.
To massage, stretch, and strengthen the fingers of both hands, start this video at about 4:30 and you can follow along and learn some fun exercises.