What is the best way to handle and release them?
You can grab them by the jaw…but the bigger they are, the harder this is, since they seem to develop a broader, harder toothy pad on the upper and lower jaws as they grow. Also…it hurts like heck when a decent-sized one clamps down on your thumb!
A Boga-style lip gripper or net would be useful, but I tend to fish “light” and often leave these items at home.
For the ones less than 30", I generally hold them with one hand across their back, ahead of their dorsal spine, and a gripping just behind their pectoral spines. Bigger ones…I grab their lower jaw and hope they don’t clamp down!
lol… I’ll lip any flathead going but I am done sticking my fingers in the mouth of a channel cat or blue of any size. 
After 50+ years of catfishing, I’ve easily handled tons of catfish.
As Dave says, any fish up to about eight pounds I just grab behind the dorsal and pectoral fins. I’ve landed channels up to 20 pounds by just reaching down with both hands and grabbing the pectoral fins. Actually, it’s those little fish you have to be careful of - especially releasing them. Just about the time you go to give them a toss they like to clamp down with those pecs and will open your finger up like a saw blade. And not much will be more sore for a few days.
Don’t fall prey to the old wive’s tail about rubbing the wound on the fish’s belly. There are people who swear by it to this day but it’s been proven it just rubs bacteria into the wound. Release? They are tougher than an axe-handle. Just get them back in the water. They’ll be fine - just don’t get hurt doing it.
Oh yeah… Welcome to catfishing.
I use a Boga Grip. Works great.
I handle them with a large cast iron skillit butter and lemon
Angled channel lock pliers with the tips duct taped…used them for years on the Ohio River…they might croak at ya but will not be any less the wear using the pliers…plus, the are cheap…
Easy:
If you can see the fly, grab the fly with your hemostats and shake the slimy thing loose. A quick flip of the wrist usually does it.
If you can’t see the fly, cut the tippet close to the mouth of the fish. It will swim away.
This way you don’t have to touch it at all. The only fish out there slimier than a catfish is a trout. I try not to touch them either.
Nasty, slimy, smelly things! YUCK!
Buddy
anytime I’m fishing I always have a gardening glove in my backpack and I just put it on and lip em. I been stabbed by a few small ones and they hurt like hell LOL
Fatman
OK folks, this is really easy. if it’s small enough just use the hemostats and pop the fly out. Don’t try to grab it like below or you’ll get horned.
The bigger ones (eating sized) have built in handles:
-Facing down take your hand and CAREFULLY slide it up behind the dorsal fin until the erect dorsal fin is nestled into the “V” between your thumb and forefinger.
-Take your thumb and slide it up behind the pectoral (?) fin on the thumb side
-Take the ring finger and middle finger and trap the pectoral on the other side.
Instant three way handle. Very secure and the only real danger is from the dorsal fin. If it’s big enough that the dorsal fin is taller than your hand, no worries! Plus if they’re that big, the spines in the fins are no longer sharp.
Bigger cats you can grab by the lower jaw if need be. They may clamp down on your hand, but it’s not like they are snapping turtles…
Slide hand under belly. Slip 1 pect. fin between middle and index finger (or middle and ring finger, palm of your hand across belly, thumb behind other pect fin. There is a bone at the base of the pect fins that you anchor on. This keeps dorsal fin out of the picture. Can handle up 4 - 5 lbs. this way w/ 1 hand. bigger ones need 2 hands - second hand across back w/ dorsal fin between thumb and forefinger. Risk of getting stuck is actually greater w/ small fish
I do not release channel catfish, I attach them to a tree by pounding a nail through their head, then peel the skin off the body, from behind the head to the tail. Instant catfish fillets.
Then you mx up some batter to dip them in before deep frying them, and make some hush puppies, and some cole slaw and a bucket of cold beer.
That is what I do with catfish.
And that ain’t no bad plan. 
Yo Buddy!
For the slimy award not much beats a Burbot. A trout would be 2 on the 0-10 slimy list a burbot 10+. When skinning them you actually have to clean the two pair of pliers needed to do the job after every 3rd fish or you will no longer be able to hold on to them. Nasty ugly creatures that just happen to be anong the nicest tasting of fresh water fishes. They are also among the hardest fish to kill.
Now, on catching them, remember, just jump into the water, preferably where the current has cut into the river bank, hold your breath real good and go underwater. Probe around with your bare hands in any hole you might find there and if you feel anything, just thrust your hand in there and grab it … anywhere! Should it be a catfish, just hang on! Now if you do make it to the surface and decide you don’t want the fish … just let it go!
Did I leave anything out …?
Best way to handle them is with a Deep-Fryer, and Fries. I don’t know about the release thing. I don’t think I’ve ever done it…
Why in the world would anybody want to release a Catfish…probably the 3rd most delicious fish there is, right after bluegill and crappie (Walleyes get Honorable Mention)???
The real question is…will the catfish let you go???
I Had posted that because of seeing a documentary on television sometime back about these guys that would just do that monkey business of going into the water after big catfish bare handed. Some of them had missing fingers, all kinds of scars, had got hold of who who’s what and, of course, someone drowned, too. Now that had to be a dedication to a “sport” that would make us flyfishers pale in comparison!
I with CharlaineC Cast Iron all the way.
I bought a pair of butchers gloves from my butcher. They use them so they do not cut themselves with the super-sharp cutting knives when they are butchering meat and fish. Not that expensive, and fit in a pocket when your fishing. Really useful when you catch a Pickerel, Northern, or Muskie!
The gloves also has a grip grooves for securing your grip.
~Parnelli
Roger that!