The article was the easiest I've found involving the construction of a homemade sand bag using my green canvas bag from basic training. 20$ worth of rubber mulch from Home Depot and I was done.
ITS Sandbag Training/Building Article
So I got mine up to the recommended starting weight of ~60 Pounds. Afterwards I decided to test it out with 10x100m sprints (50m out/50m back), with about a minute rest between. Fairly brutal way to start it out.
Later this evening I'll get into some of the other movements and see where I stand with them. A whole laundry list of shit to do with a bag can be found in the previously linked article, and a video to boot.
If you're also interested in other knowledge of tactical shit, self preservation and general usefullness I recommended browsing around ITS Tactical and maybe even picking up a Crew Leader membership.