Those will work, but I like mine much smaller and thinner which gives me more surface area for a given volume of char.I found some charcoal online to make bio-char, and ordered one test bag.
Are these fragments the right size? (The bigger chunks settle to the top, but I was expecting smaller fragments...)
Are these too big? Or just right (and soak 'em up with EWC)?
To charge mine I've done it a few different ways. Like you I've mixed it 1:1 with worm castings and let it sit for months, but if I need some quickly I'll submerge it in a soup of worm castings tea and several of my Jadam extracts. It will bubble like crazy for a while as the air is driven from the char and replaced with nutrient rich liquid. I try to leave it at least a week or two when doing it this way.