I haven't done much in terms of dojo/classroom threads for a long time... mind, a lot of what I used to participate in was one-on-one, with the occasional group training thread that popped up here and there.
They can be some of the easiest threads to set up, and some of the hardest to keep going unless you can appeal to your audience, maintain pacing, and make the subject interesting/fun.
Last training thread I actually participated in with Rik, here, was on Shatterpoint a couple years ago, and I rememeber it reasonably well. Making rocks break apart/explode is kinda fun. Getting pelted with bits of rock for the first several times sucks for your character and those around them... which is also part of the fun, until you figure out how to mitigate that, or not.
And enticing if you realise the further applications. Ever heard of ballistakinesis?
![Wink ;) ;)](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)