I will definitely give a plug to the “Impact Snap” training aid. It’s small enough to keep in your Teaching Bag and quick to use.

My favorite is using an impact bag. However I fill mine up with about a Third of sand and then add packing foam. If you really want to work on the impact position the impact bag has to have some density to it so that you can really see where the club is at impact.

I also like to use and old tire. because it just isn’t going to wear out. You just have to be careful with the tire, if you don’t do it properly you may get hurt. Additionally if you use the tire, get an old club. I have definitely had some shafts bend through the years.