Nail them thru the middle of the skull to a tree, pole, or a sturdy board with a large framing nail. Cut off the fins and cut the skin just behind the gills from the spine to the edge of the belly. Just the skin. You do not have to cut deep. Loosen the edge of the skin near the spine, clamp on the loose skin with the pliers and pull the skin off.
With this technique gutting is unnecessary.

Oh.. Since this is a cooking thread. ..after you filet the fish grab some Zatarans breading and follow the instrinstructions.

I prefer predatory catfish like flatheads for eating. The scavenger types can be gamy.

I live on a canal & I can pretty much catch as many as I want whenever I want.

I just cut the heads off, clean out the chest cavity, & toss them on the BBQ grill. The skin peeks right off after they're cooked.

Skin comes right off after they cook. Not a big fan of cat fish, except for bullheads, love them.