I don't play any string instruments, I did this pick for a friend who plays the bass, I guess this kind of picks should be used with instruments that require high pressure on the cords in order to play, I can't give additional information about the ideal pick for each person, I just can say it's easier to work with a 3mm aluminum pick and it's easier round shape with it.
You will need:
-Aluminum sheet (3mm works best).
-Sand paper (150->200->300 or more)
Engraving part (optional):
-Paint (I chose black)
P.D: Sorry for the mess.