Wet your hands. Don't use a tailing glove. Better yet, don't take the fish out of the water! I try my best, honestly I occasionally don't wet my hands if I feel taking the time to do so puts the fish at risk... but those are rare circumstances. It is not worth photographing a fish if it dies as a result.
If you look at my blog posts, there are a lot of pictures of fish being held in the water, or even post-release. Frankly those make for far better photos. I reserve the "grip-n-grins" for carp and big specimens of other species. In pretty much every of the photos where I am holding a trout, you will see that my hands are wet. If you aren't going to hold the fish for a picture, wet leaves and moss are decent, but don't let fish flop around in sand or dry leaf litter if it can be avoided.
And don't take a picture of every fish you catch! If I did that there would be a significantly greater amount of photos in each post. For example, on my first day ever fishing the Farmington River, I caught roughly 10 fish. I took pictures of two. The very next day my catch exceeded 15 but I only have pictures of a wild brooky, one brown and one rainbow from that day. Nobody needs to see the photos of all those other fish, do they?