Should point out this is for roll and spey casting, and essentially simulates the drag you get from water to form the Dloop.'Grass casting' is not unusual at all but you need to make a grass leader. Basicly its a leader with 4 to 6 inch 'tails' at a right angle from the base leader.
Longer the grass the shorter the side pieces. The down side is it works but grass casting will ruin the leader for actual fishing.
I been asked to 'pose cast' a few times by tourists, once bus full of Chinese thought I was what they were stopping for, after photographs they all thanked me, makes a nice change from the local grunters.Have done this quite a few times. Not much interest when I was doing it early - depends where you go. If there are tourists around they will probably love it and you might be asked to do a photo.
Or the old busy body who calls the constabulary about 'some strange man whipping something in the park'.Be aware of over zealous "jobs worth" park staff who might try and stop you! I had this when living in Edinburgh and casting in Inverleith Park. I pointed out it was no less dangerous compared to people power kite flying and skate boarding in the park!