I really don't know if it "has" to be Johnson's... that's just what the "big boys" over at Cast Boolits say to use.
The way they recommend blending is to melt the paste wax in something over very mild heat, like a double boiler... I just used a hot plate turned down low... melt the wax, and let it "cook" for a few minutes. Don't get it hot enough to really smoke, just almost smoke, if you can do that. Once it cooks off whatever solvents it's cooking off, you add an equal part of LLA, and stir them up together. Then add your calculated 10% mineral spirits to thin it a little more. Stir it all up, then let it cool off.
To be honest, I wasn't very anal about the quantities. I got pretty close on the 45-45 part, but didn't really calculate exactly how much of the mineral spirits to add... just put some in.
I'm gonna load some of these up and give em a whirl, hopefully this weekend. I'll post the results, if I do.... just don't laugh at my groups. I'm still working out a good load for cast boolits in my K-Hornet. And I'm trying three different boolits.
Keeps me off the streets, though...