Desensitizing exercises

What are some good desensitizing exercises you do with your horse?

I have strung plastic shopping bags all around my roundpen in various locations around the pen then changed up the locations every few days. This I did with the older horses here. I, honestly can not put into written detail how or what I do to train for a specific response from a horse. I just do what comes naturally.

I am humbled by what a Vet remarked about my mare's second born filly. We had trailered my mare and the filly to get blood drawn for Coggins testing. He said, he could tell we had put a lot of time into handling and working with the filly. Our third born filly was a bit more determined to not being as eay to handle as the previous filly.