Seems I have to give everything away?
The jig will get through that relatively thin cover easily. Let it fall to the bottom with a thump. Usually the bottom in this type of cover is muck or silt. The jig hitting it will send up a puff of fine sediment- it looks like a puff of smoke.
That gets their attention. Next, lift the jig 6" off the bottom and, ever so gently, twitch it in place for maybe 3 seconds (5 or 6 twitches). Hold it steady for another 2 seconds- if they haven't taken the jig by now- there are no fish there OR they have lockjaw. Retrieve your jig and make your next pitch or flip.
Now, when the fish are really active (not often enough), they'll be on that jig within a split second of it breaking through the cover and you won't get to try the old seductive jiggle and twitch. They'll hit it hard. Be ready.
With the proper rod and jig in this type of situation you DO NOT rear back and set the hook like you would with a T-rigged worm. You simply lift quickly and smoothly. Get the fish up through the cover before it knows it's hooked.
CCB