I tried copying the photo's but the only way I could do it was to left click the picture in the album, then mouse over the picture and left click to enlarge it, then hit the PRT SC button (print screen), then open up paintshop and then hold down CTRL and then hit the letter V and the picture should then paste into paintshop. Then you can move it around, trim it, whatever and then save it as a file.
I know years ago when I did not know what I do now is I was using a lot of filler (what I've been calling a bodyman in a can) and I know what you are saying about edge thickness variations or a filler edge. I know on my doors, I would first get an idea what area's needed to be raised or lowered and did what I could with body hammers and dollies but it got to a point that I could no longer feel issues so I then shot the area's with primer and with a paintstick wrapped with sandpaper, started sanding the panel. If I started seeing bare metal appear I would stop and work the area down with a hammer and dolly and then sand some more. If I saw spots that the sandpaper did not even touch, I would raise the area again using my hammer and dollies. Eventually I got to the point of not breaking through down to metal and having the sandpaper scratch all of the panel.
Since I'm a novice, I had tried using my air file in spots but kept chasing issues as I could just not get it to work with the foam backer so I bought another sled, peeled off the foam, took some 1/4" thick plexiglass and cut it to be where the foam was at originally and glued it on. Now I had a hard surface on the backside of the sandpaper and got it to work better for me that way. I've seen guys using the air files with the foam backer but I just could not get it to work right OR I was expecting too much or did to much with it before switching sanding methods.
Another thing I used was Grandpa gave me some old lead files and they were perfect for wrapping sandpaper around them and using it to have a rigid sanding board. Granted they are only about an inch or so wide but it worked for me. Today, you can buy all type of sanding boards but I used what I had laying around.
Jim