I wouldn't recommend using a downrigger at all. Use a Columbia River style salmon rigging. On your mainline slide a tee,bead,slider(for dropper weight), another bead then tie on a bead chain(6) with a duo snap. Use an 18-24" dropper for your weight and a heavy 24" leader from your bead chain to your fish flash. From your fish flash you can run a mooching rig of your choice of length with a cutplug herring on it. Leader length usually depends on clarity, the clearer the longer. I like to use a Dicks Surespin helmet for herring as it protects the bait and makes it last longer. As for grass you just have to deal with it. There are some companies that make a plastic sleeve to go over your bead chains which keep them protected from the grass and help ensure everything stays spinning and doesn't foul up or tangle. You should use bead chains in front and behind your fish flash as you will have lots of spinning gear down there and they will keep the tangles out. Use appropriate weight to keep your gear down based on current/tide, anywhere from 8-16oz. I like to fish near the bottom. Let your gear out slowly, too fast and you risk tangles on the way down or when your gear hits the bottom. I haven't been out there yet this year but that is a standard rigging for the bay as well as Buoy 10. Good luck! Have fun!
