It *is* best to exercise a lot of caution when catching cories and pictus. By the by, since when does the pet store have the fish's best interest in mind? They use a net because its cheap and easy, but caution is always better in my mind.
I've heard people say (when catching big spiny plecos) that an old crappy (clean) pillow case can be cut to fit just like the netting on your standard net. There are no holes to get tangled up in. And pictus are scaleless so you have to be careful with their skin. Basically, I'd think any soft cloth would work, provided that it's clean. Some people also use a container underwater, but this can be difficult with such a fast moving fish.
For the record, too, I've personally witnessed Brochis splendens get mangled in a net at a local pet store. The lady was an idiot so I told her to let me take the poor things out of the net with a pair of tiny scissors. A bushy nose that I was buying at another store also got very tangled up in his nosey bristles.
That said, I had to move fast once and used a standard net to get my pictus out. He was unscathed.