Been a long time since I've fished up there, but sand eel was the bait for the doggies, makerel for the rays and conger, even the odd tope, and crab for the bass etc.
Most of the comps were fished on the east side of the loch at the likes of Cairnryan, and all the way up to the mouth of the lock.
On the west side, I have had a few bass from Lady bay on crab. There should also be a good chance of pollock in the same area. The entrance to the loch was good for nice plump plaice, and anywhere you can get access to the rocks leading to Dally bay which is out of the loch and westwards.
Hope this is helpfull.