Hiya
There are a couple of ways to catch them with a rod.
Firstly, you need a long handled net. This is because crayfish will hang onto a bait until it gets pulled to the surface, where it will then let go of the bait. The idea is to pull the bait up slowly, then push the net under them!! Try using BIG baits, like a whole fish (anything from 500grams to 2kg's) or fish heads (snoek or yellowtail, etc)
Another trick is to put lots of sardines/pilchards in a stocking. Then Fold the stocking over itself a couple of time. Also put a large sinker in the bag. Now tie it to your rod or bamboo pole. Drop it into a kelp-bed or rocky area. The crays will attack the bag, trying to get at the food on the inside. In the process, they get caught in the stocking/pantyhose, much the same way a broken fingernail snags in the material. Simply lift the bag out of the water!! This option works well when you don't have a scoop net.
When using hoopnets, from either boat or shore, ALWAYS try and use OPEN baits. That is bait that is NOT put inside a bag. The open bait gets eaten off rather quickly, so take lots with you. (small hotties, stumpnose, steentjies, ANYTHING!!) They attract MUCH more cray's than normal bait in a bag!!
If you really want fun, trying diving for them. A wetsuit, mask and snorkel, weightbelt and flippers is all you need. MUCH more FUN and you can also select the biggest ones, which seldom want to take bait.......
Here's a pic of some westcoast Kreef, taken out diving.