First off, I'm going to be really annoyed with myself for not wearing my EDC neckpouch - my whistle is in there, as well as my credit-card sized Doug Ritter Rescue Flash signal mirror! But more seriously ...


Absolutely, many of which I've had much better luck with than the Vee-finger method, and none of which work nearly as well as a retroreflective aimer.

If I were training multiple methods, my priority list would be:

• How to use a retroreflective aimer mirror (and recommend carrying one)
• The "sighting hole plus touching fingertips vee-notch" method
• The "mirror corner plus touching fingertips vee-notch" method

I think the "mirror corner plus touching fingertips vee-notch" method (2nd to last) should replace the "Vee-finger" in training. However, there are lots of people on this website with far more experience in training others than I - so I'd be interested in hearing their take on that suggestion.

If I don't have a retroreflective aimer, the first thing I'd try to do is to put a hole in that reflective material so I can use a precision foresight or double-sided mirror aimer.

The classic (1800s) way to do this is to put a hole in the reflective material to sight through, catch the "shadow spot" in the reflected rectangle of light caused by the non-reflective hole, and line those two up with the target.

Sighting hole plus touching fingertips Vee-notch front sight

This is the "improvised aimer" technique I've had the most luck with, both using it personally, and teaching someone else to use it successfully.

• Years ago, I augered a ~1/4 inch diameter hole in the back of a CD with my EDC pen-knife, used that as a sighting hole, and my touching pair of index and center fingers as the foresight. I looked through the hole, held out my hand to put the target in the "vee" atop my touching finger tips, tilted the mirror to put the shadow cast by the augered hole on the contact line between my two fingers, then tilted the mirror to run the shadow up the contact line and onto the target. It worked quite well (except for my wife's comments about the brightness compared to the Rescue Flash) - I count about 42 flashes in 52 seconds - here's the video (You'll probably need to click the YouTube icon at bottom to get the video large enough to see the flashes:
  
  
• I taught my coworker this "two contacting fingers and sighting hole" method, and he signaled me quite successfully (I called out 20 flashes in 42 seconds, though I see more in the video) at 22 miles using a manufactured 2"x3" metal mirror with a ~1/4 inch central hole as the sighting hole (The mirror manufacturer had recommended the "vee-finger" method, but that's my very last resort until someone teaches me how to do it effectively). He also did quite well at 22 miles with my CD from the prior example (I loaned it to him). At this range, the mirror wasn't quite bright enough for naked-eye visibility, but it shows the targeting method just fine.
  
  
• If I can't punch a hole - can I scratch a window? Yesterday, I tried using a glass mirror (like one you might scavenge from your car vanity mirror) with a 1/10" hole scraped in the silvering (a pushpin works well, I imagine a knife point and patience would, too. With that small a hole, the "shadow spot" was pretty faint on my finger - the white back of my health card from my EDC showed the shadow more clearly. I hit my license plate target at 60 ft the first time 20 times out of 20 (dropping my hands to my sides after each try).

Improvised double-sided mirror:

• 
  I haven't tried these, but the US Navy recommmended the "double-sided mirror" (they called it "rearsight") approach (diagram in an earlier post in this thread) as "a method which readily can be improvised for signaling with different mirror materials."
• "A flattened piece of tin can may be used after a hole is punched in it."
• "A flat piece of glass or clear plastic can be aimed by the rearsight method if a piece of opaque sheet material with a hole near the center is held in front of a small part of the whole transparent mirror. That part of the glass behind the opaque sheet material becomes the part of the mirror used for rearsight aiming.

If you can't find or make a hole: touching fingertips Vee-notch front sight and mirror corner

If I can't make a hole, the next best thing is the corner of the mirror, because I can locate the corner of the reflected rectangle, and the corner of the mirror, and get my eye, the mirror corner, the corner of the rectangle of light, the notch between the touching fingertips of my index and center finger, and the target more or less lined up, with the main parallax effect being that I can't look through the corner of the mirror, so I have a small offset. That's okay - that gives me the axis I need to wiggle the mirror for flashes. I tried that at short range yesterday, and it worked okay. The closest to this I've seen elsewhere is in "Outdoor Safety and Survival", by Paul H. Risk (good resume and collaborators), Wiley, 1983, Fig 5-2, page 57 who mentions sighting along the corner of the mirror with a thumb as a foresight.

Shaded tree limb or the like many feet away

Often recommended - I think I could get this to work in the right circumstances.