I use my camera in the field (if you have one), then back to camp and use lap top for larger viewings.
This does not work, in some cases, for those who have game cameras that do not save the images in a DCIM directory. My hunting partner had this issue and could not figure out why his camera sometimes worked and sometimes didn't work for reading cameras. When I checked the game cameras, I discovered that his camera would not read only specific game cameras and the reason why was the directory issue. That was the only difference.
I have an old digital camera that doesn't care. It will find all of the images on the SD card, regardless of the directory structure/naming.
I've been looking at the ones on Amazon that plug into the power outlet on your phone. I'm kinda looking for something small like that but I'm not sure how they work or if the work all that wells
For Android phones, they need to have OTG or USB HOST capability. Apparently the Samsung Galaxy S4 (mine, old phone) and S6 did not have these capabilities. The S7 (what I have now) certainly does.
I use ES File Explorer to go through my images on the external card reader. It works very well and is quick.