Don't be afraid to go light on the yellowtail. I use 10 pound test fluorocarbon on a spinning reel with a very small hook. Get your chum going good for about 15 minutes, draw them up and hide a a small piece of squid or cut bait on a 4-6 Octopus Hook and free-line the bait. You can also have a second chum bag sunk below the boat at about 12-18 feet.
As for dolphin, I love catching them on 15 pound test. I find a group and throw out a little cut bait to get them excited. You can catch them on slabs, jigs, MirrOlures, 1oz. Rat-L-Traps and a variety of baits by casting (don't forget topwaters - they are a blast). We do usually stick with 20 pound test and trolling for bulls.