In practice, I think it helps to have a target at the mirror location so you can simply shoot the object ball to that target. If the goal doesn't change -- such as the center of the foot rail -- the mirror target can stay in the same place for a bunch of shots with the object ball starting in many places.
The way you constructed the mirror target was not quite correct. The reflection point is the rail groove. Maybe a minor point, but I think it is better to get all the details right.
That's a good point. I think I will make a follow up video and correct it. I didn't want to make a target at the mirror location such as a spot on the wall because I was trying to show my method of "bouncing" the cue to find the spot.
But your tip is absolutely the nuts. Not only for practice where you can set up a mirror target at will but also in game situations if you are able identify key landmarks around the table that are in line as mirror targets then you can use them from any position without the need to do all the cue waving.
Thank you.