Shokeys has been around for quite awhile now in many forms and names. It's been branded as CleanShot, American Pioneer, and god-knows what else.
I used it as CleanShot for a couple years - until Triple Se7en came out.
The Shockeys, CleanShot, etc IS a very clean shooting powder. One day on the range I fired over 30 shots without even running my usual spit patch between rounds and never had a bit of trouble with fouling build up. That's the good news.
The bad news is:
1. It is very underpowered. To get a load equal to Pyrodex RS in my rifle, I have to add 10 to 15gr more of the Shockeys in ffg cut. Hopefully your 3fg cut won't be quite as underpowered. In 2fg cut, it takes 25gr more in my rifle to equal my Triple Se7en loads.
2. It is EXTREMELY hygroscopic - i.e. it sucks up moisture from the atmosphere faster than a sponge. I literally had a pound of it go bad on me overnight - and that is with it kept sealed in the bottle under air conditioning.
I did buy a bottle of the 3fg American pioneer awhile back to play with in my 1858 - so time will tell on how it will work with it. But for plinking like you want to do - it should serve you ok.