A method I have tried,in attempt to get a meeting point between what is shown in the video linked by asemery and what written by knot4u:
make a loop like this:http://notableknotindex.webs.com/slippery8.html
performs all exactly as in the left image, but in order to obtain a large loop, and that, what is the SPart in the figure, becomes the tail(reversed version);
continues to hold the loop so obtained in front of you in the same position as shown in the image on the left;
now rotate the loop in front of you,so that the tail of the loop (the one you just went through the figure of eight) points toward you(quarter-turn counterclockwise looking from above);
pass the object through the loop held in this position;
adhere the loop around the object by pulling its tail in a relatively mild manner(during this step is not necessary that the figure of eight is tight);
Now pull the tail of the loop (which still points to you) with energy, in the opposite direction (see at this point that the figure of 8 tightens and capsizes),until tighten around the object as desired;
If necessary, run a pull too on the other tail,to fix everything well.
In doing so, I think he can quite easily tightening the object by only pulling this tail, more or less as shown in the video, and that should be quite easy to untie the knot, as is usually the way to being untied the gripping hitches(more or less).
If it is not clear let me know! I'll try to explain myself better, and it remains obvious that I'm curious to know what the limits and flaws of the proposed here.