Note: Since I only have a small multi chopper, not a blender, I do smaller quantities. I'm pretty sure a hand blender would do the trick as well. Also, personally I like it better when it's 1 part oat / 8 parts water approx (not 1/10 as shown in the video).
I mix the oat with some of the water in the multi and when it's done, I mix this content with the rest of the water in a large bowl. I also make sure that the water is cold and I stir for half a minute or so.
The cloth I use for the draining comes from an old worn out t-shirt, that is consequently very thin, and is dedicated for this use.
I find it's important to shake well the jar or bottle that the oat milk is in, before each use.
The leftovers in the cloth, either I just have them for breakfast with raisins and nuts, or I use them to make cookies.
Even if you make a mess or it doesn't work well the first time, maybe it's worth giving it another try. I think it's a super cheap experiment to make and super cost effective in the long run.
There's recipes out there for using the leftovers for bread too, and they're pretty good
If you have a specific one (or more!) in mind could you please share?