It may be that you did not add enough water to allow easy separation, you want to add about 3-4 times as much water as there are solids, that way when you shake it, you should get good separation within 10-15mins, more than that and the yeast will start to settle out.
Sounds interesting and post pics for sure, however, a couple of glass jars are cheap (free) and easy to (heat) sterilize.
I've never had a problem separating yeast this way so for me I don't see the need for a 'device' to do it for me, especially if its going to be harder to sterlize, especially when I can simply tip the jars to decant the yeast/trub as required. If it was something that was used very often and easy to sterilize it might be worth the effort.