I did it a few times when I was a kid. The secret is to NOT dry it in any way but sunlight.
Mix your powders wet so they can't blow and combine them like a black bread dough. I used a cardboard box and set it in the sun for 2 months and then ground it using pieces of about the size of a walnut, one at a time until I got the granulation. Last I sprinkled with graphite and mixed it in small batches. I never had a problem but I was VERY careful and never worked on dry cake in any piece larger than a walnut at one time I figures if a walnut sized piece blew when I held it in my hand (with welding gloves on) and my face was covered with a shield I'd be ok.
Might soil my shorts............but still be OK
