Well I'm still finding faster and faster ways and it depends I guess on your software.
I have about 10 photo editing software programs but normally just use PhotoImpact as it was free a few years ago.
I also have Photoshop Elements which I think allows me to "Ghost" or layer one image lightly (transparent) over another. I'm still playing with that one.
Anyway I've put a couple of reduced images here as my actual Perf Gauge scan is about 2,500 pixels tall.


same shot large size screen grab:

For now I slide the stamp over the gauge (take a copy and paste it to the gauge and move it abut, but don't save the picture).
Ultimately I'm working on just having the gauge as a "transparency" (25%?) to slide over the scan of a page of stamps and just make notations as I go.
Or I can "erase" the white areas of the gauge away just leaving the lines to move over the stamps.
It also saves worrying about damage to dragging a stamp over the gauge or bending due to positioning using the tweezers.

And if you eyes aren't to good then having a stamp the size of an A5 sheet of paper is so much easier!
Actually I just had an idea! When I get the transparency idea working right I''ll just load a jpg picture of it here ( and if anyone wants the large format one or I'll email it out) and then anyone can use it themselves. Just remember to use the same scan setting of 600dpi. (Don't use the gauge above as I shrank it)