What can i expect to catch fishing into a dubby slick

I'm going to be fishing the inner harbour for blonde ray using a dubby bag which i will drop with the anchor. I'm going to get a bit of a slick going on the mid to top water area too and try to pick a few gars up in this and whatever else while hopefully waiting for the ratchet to start singing out to me. What other kind of fish could i expect to catch fishing into the slick and what tactics would be best. I'm guessing float fishing but if anyone has a bit of experience and a better idea i'd be glad to hear from ye. Also while i have the dubby mixed up i'm going to fill a few swim feeders and fish them off the top of a 3 down for the flatties. Anyone tried this off the boat and is it worth my while.

Thanks for any comments and tips. I'm not at the boat fishing for long so i'm still coming to terms with the different types of fishing so any tips no matter how small will be considered and most likely employed as i'm not catching much in recent days and i'm running out of ideas.

Cheers,
Evan