If your not going to use a fly rod I don't think it's really worth it to try using flies. There are plenty of lures for regular tackle that would be much better suited to a spinning or casting rod than trying to make a fly work with it in my opinion. The only effective way I've heard of fishing flies on a spinning rod is under a float and I don't know how effective that would be for redfish and trout.

Look at johnson silver minnow spoons and DOA's soft baits to get you started.

If you do try it though, I'd be interested to hear how it goes.