All you need is a billy, a good, sharp fillet knife and good fingernails.
Whack the fish a good, solid whack to make sure he doesn't flop around while cleaning. (On the head, in case we have amateurs reading.)
Place the fish on it's left side and make a deep cut to the backbone and down to halfway around the fish right behind the gills and in back of the large bone found there.
Place the fish upright, start the cut tight against the rear of the top front fin. (We're doing the right side of the fish first.) (It's been a while so bear with me.)
Keep the blade tip tight against the fin and punch the tip in, work down to rib cage, no further, then work forward to the previous cut.
Deepen the whole cut to the rib cage, then at rear of rib cage work blade down to vent, keeping the blade tight against the backbone.
With blade pointing toward tail, work the blade toward tail, keeping it tight to backbone all the way.
Use your thumb to peel meat back from rear of rib cage and slice along rib bones, fleshing out meat along top of ribs to the front cut. You should now have a nice fillet, very little meat wasted. Basically repeat the process on the other side.
To skin simply use knife to start cut at tail edge between meat and skin.
Give yourself at least an inch to start with and grip with fingernails pressing down on the skin to hold in place.
Work knife slowly back and forth while keeping a forward pressure on and even fairly large cats, say 12 lbs. or so will skin easily. (Sorry, I don't want big fish so you're on your own with the big ones.)
The knife must be sharp and you keep inching your fingernails up on the skin as you gain ground.
You end up with a very nice fillet, no "silver skin" for fishy taste or curling up when frying.
I never cut the tails off to "bleed" as I've seen many people do. Once the fillets are cleaned, keep hosing under pressure with fresh water and all the blood will wash out in a minute or two. Larger fillets, wash one at a time.
Keep fish in water and ALIVE until cleaning. ALL fish have the bacteria on them that causes rapid spoilage and they start spoiling before they are dead even if they are not kept under good conditions. (Live box.)
I hate to admit that I used to turn up my nose at catfish until I started catching and cleaning them myself. For a Minnesotan this is heresy but I now prefer them over Walleye and so do my neighbors.
Catfish from some waters are not as tasty as others though. I think the available food supply has more to do with this than water quality.