I use external key pads. A Logitech G13 (for Lightroom) and Genovation MicroMaster 683 (Photoshop). I find that they greatly increase my efficiency.
For your problem I have three keys in a row: Previous, Copy, and Paste. Under those keys I have Enter. I would, on the file which would be Previous, hit Copy, check to see that everything is checked except Crop, then press Enter. Now press Paste. Usually the Copy settings are as you want them because you have been using it for other files for the same operation.
Or set Copy so that only Crop is checked. Press Copy on the working file to get the crop. Then press Previous and then Paste to revert the crop to what you want.
This can be done from the keyboard but I find it awkward, the keypad is much faster. I hate the ctrl-alt-shift stretch and crossing the left hand to the right side of the keyboard is a no no. My right hand is always on the mouse, so any key presses are done with the left hand. This means keys like the arrows and Enter are awkward and they are therefore on the key pad