I ask my WS and tool shop guys all the time.
I have been using a small diamond wheel on an air die grinder for a few years now. Guessing the angle has been fine up till now.
I like different angles on my tungsten for different materials and also for weld type and available room in joint area.
I would like a trick looking sharpener that gives consistency without thinking about it too much.
This will be the easiest build I could think of.
I am sure others have even better ones that they have fabbed and I hope they will post images of theirs too.
The total cost of materials $3.00