None of them are particularly easy, especially on a small scale.
Lysmata spp have had the most success, but its work and they tent to settle around 50 days after hatching. Mostly breeding any kind of shrimp is difficult on a small scale, especially if you want regularity. Large scale is different - get a ton fo shrimp, stuck them in ponds and let nature take its course. Fresh and Saltwater 'ghost' shrimp are raised in big ponds, as are some kinds of food shrimp.
Here are some small scale links:
Breeding Journal, Species: <Lysmata boggessi>
Other options include amphipods, mostly gammarus, should be collectable along any ocean shore in the world - you just have to poke around to and see if you can find them in enough numbers and the right size. Gammarus are also available commercially, at least in the states and Europe.
Fish are also a possibility. Poecilia sp (guppies, mollies and sailfin mollies) can be acclimated to salt water with various degrees of success, and their gut loaded fry can be used to feed cuttles, though I don't know anyone that has used them as a sole food source. Again you run into the problems of ease and scale - you can't just grab a couple of pair and generate enough fry to feed out on a regular basis. http://www.guppies.com/forums/showthread.php/33610-Marine-Guppies-(Full-Saltwater)
The major issue of breeding food for cephs yourself is the scale needed to make it reliable. One rule of thumb (and I don't really like these rules of thumb) is that you will need 4 times the water volume of the animal you are trying to feed to raise the feed animals. Essentially, you get into the food raising business which can be very time and resource consuming.
I think thats all the tricks I have. Feeding any marine animal offspring is the major stumbling block in any marine species breeding, so know that we are not alone in the ceph world with this issue.
All that said, I hope you or we find a simple, practical solution to this problem.