Aiming Signal mirrors is hard
Why you really want to use a "real" signal mirror aimer rather than the "form a "V" with two fingers" (vee-finger) method.
Most people don't realize how hard is for a signal mirror to hit a target at long range. The reflected rectangle of light at very close range is deceptively large, since it is dominated by the size of the mirror.
However, at long range, the size of the mirror has negligible contribution to the width of the beam ( even if it were a foot on the side - can you see a 1 foot wide object a mile away?) What determines the width of the beam at long range is the divergence of the beam due to the angular diameter of the sun. Since the moon is the same angular diameter (think "total eclipse'), and a lot easier to look look at, I've used it here, together with a small 2"x2" mirror reflecting a beam into shadow for comparison.
Good commercial signal mirrors with retroreflective mesh aimers can be found at REI for $10 or less.
If you are buying elsewhere, be wary of mirrors with non-functional mesh - see the consumer advocacy article here: WARNING: Phony Glass Signal Mirrors
If $10 is too much for you, you can make a very good signal mirror aimer, as shown in this YouTube video: DIY SIGNAL MIRROR
Okay - now you're going to say you can use a CD. You can, but at range it is dimmer than the much smaller plastic "rescue flash" mirror and much harder to aim. If you must, though, see this video here, which (as text) includes instructions on an aiming method that will at least let you hit the target at long range.CD as signal mirror - 11.1 miles