I've done the trip 5 times, via Ferry 4 times, and boated there once.
Are you boating up to Shearwater via Hardy or Bella Coola or are you taking the ferry? Tent, Camper, or Sleeping on Board? The road to Shearwater is under water most of the year.
Shearwater is a great place to base out of for Milbanke Sound. Generally Shearwater sends their fleet to the St John's Harbour area, however I have been there years where they favour Cultus Sound (think Spider Island) or McInnes Light (long run, open water). For the most part you cannot go wrong fishing anywhere from Cape Swaine to Cape Mark. You will quickly figure out the hotspot there by the number of Aluminium Lodge boats. I've had great success in other areas though so don't get fixated on that one spot. Other areas work a try are Ivory, and (Billy) Idol Point. The run to the outside is about 45 minutes, past Cape Swaine (very lumpy usually) the water flattens out a fair bit to St John's Harbour. Go there and beyond. The guides have a set trolling pattern, I believe it is counterclockwise, don't worry they will tell you if your wrong.
When the bite is on, pretty well anything works. Some guys favour Cutplug, but we found that requires a lot of attention due to all the feeders and shakers. The day two Coho followed my Downrigger clip to the surface, I found my favourite colour spoon. Anything with Chartreuse. Grab some Coyote's or Dymara's.
Shearwater has pretty well everything you need. Washroom/Showers are clean, Laundrymat. The Pub has good eats. The store has basic tackle.
Life around there revolves around the Barge. If the Barge is late, you may be waiting for Fuel or Supplies so be prepared. Keep the tanks full. Bring backup gear, especially for the Downriggers.
The campground is big gravel most suited for Campers. We tented there, but you need some cardboard or something to flatten the ground out so you don't put a hole in your floor.
Mike and Jason at the Sportfish Centre are very helpful. Their bread and butter are lodge guests, but time permitting they will help you out. I believe they will still freeze (and process) your catch for a small fee. Salt Ice is available at the Fish Plant in McLouglin Bay.
Make sure you get to know the area. The run from Shearwater towards Dryad has a few shoals by the Islands you see them at low tide but not necessairly at higher tides. Heading out Seaforth Channel is fairly straight forward there is one series of Rocky Islands that jut out significantly a few miles past Dryad. If your following the shore in the fog you'll notice their dark mass just before ... .
If your lauching there and the boat launch is blocked talk to the Wharfinger, she will be your contact for Camping and Mooring as well.
Good Luck, it's worth the effort.