Oops! I meant try putting them on the back of your cardboard or IPSC's or whatever, where you can't see them to sight on.
Place them where you want to be hitting, then shoot up the blank side fast and furious. Or faster and furiouser.
I try to do 3 and 5 yd. sessions this way, starting the fire at low-ready from draw, working my way up to sights for the last couple to COM and some to the eyes/nose triangle.
As for the holster, hope you caught the humor of a "duster" for casual cover garmet, with all the shoot-me-first discussions about my photographers vest.
I really still shoot 35mm film and have 6 to 12 rolls in all those pockets, a lens brush, etc. Sometimes I leave the Canon A2 on my shoulder for training. In a real SHTF, I suspect the camera would be on its own.