Older editions of re-loading manuals can be a great help today where you need more flexibility with powder.
Most bullet company manuals like Hornady, Speer, Sierra, etc, will devote the available space in new manuals to newer powders, and the data for the older powders is no longer included. However, in the last few years with powder being in short supply, forcing me to take what I could get, I found that dusting off some of my really old editions was quite helpful.
I've started using Red Dot extensively again, something I had not done since the mid 1980s. I dusted off the old reloading notes and loads and found they still work just as well as ever in .45 ACP, .45 Colt, 9mm Para, .38 Special and .380 ACP.
Unique is a powder I never stopped using as it is very versatile in everything from the .380 ACP to the .45-70 (with cast bullet loads). It's a great .357 Magnum powder, particularly in barrel lengths of 4" or less. Someone made a comment above that you won't get magnum velocities out of it in a .357, but that's potentially misleading. In a short barrel, you won't get magnum velocity out of a slow burning powder like 2400 or 296 either. In fact, in a short barrel, you'll get higher velocities out of a faster powder like Unique. It's one of those areas where a chronograph will tell you what is really going on with a load, rather than what you think is going on based on published load data.
Bullseye is another old reliable powder with a broad range of applications from .380 ACP to .45 ACP.