I've tried to catch scuds and they're quick little guys, not to mention being really good at hiding in substrates, so you get a net of sand plus a scud or two. this may require sifting the sand until you feel a wriggle on your finger, which will be another scud. They often climb wet fingers, it's an odd sensation. If they crawl onto a fingertip I just dip them into their tank and swish them of
If they're in a bucket, stir well with a brine shrimp net, you'll get most of them. They can stick tight to the bottom of a bucket, but a hefty swirl usually gets them swimming, or pour off water slowly 'till very little is left and then swirl,either pour to the next container or into a brine shrimp net to transfer wherever needed.
I'm just about always looking for critters I can grow or culture for my fish and frogs. It's interesting to keep the cultures, and variety does the fish no end of good.
An established population will have all sizes, from tiny new borns no more than a 1/16th inch, to half inch adults and all between. Gravid females can be so egg laden they look like some other creature entirely, but go back to normal once their eggs are gone. The size variations suit a variety of appetites and mouth sizes. My loaches and cories just love them and get plenty of exercise hunting them. Some mid level feeders will chase them too, and catch one sometimes.
I'd bet your frogs just might find them very interesting. If they are like most frogs they probably have a prey drive that is excited by movement of live prey. Scuds have a 'hopping' glide from place to place, and will sometimes swim to high levels for short times. I'd guess for ADF, scuds might be a real treat for them, not only good eating but also due to stimulating prey drive and hunting behaviours.
I've little experience with frogs other than my Floating Asian, Froggie, who ambushes her crickets and such from the surface.
You can get starter cultures of them, now and then, from other hobbyists, or from Carolina Biologicals. It's a lab, they sell cultures of all sorts of things. Look for amphipod or gammaru. I think they call it Mixed crustaceans, most being scuds, the other things are fish food too, maybe a few daphnia or such. Make sure you get FW amphipods, there are many marine species that serve similar purposes.
Have you tried California black worms ? Live, red/brown slender aquatic worms. Can be cultured, which I'm about to try, and a portion from a local store will last weeks in the fridge, with daily rinsing to keep water clean. They also survive in tanks, so no foul water, and so long as not too many are fed, they get hunted down and eaten later. They're fabulous fish food. Might be fabulous ADF food too.
I'm a big believer in live foods whenever possible and it's well known they help bring many fish into breeding condition. Frozen foods being a close second in that regard.