The ausable wulff is an attractor fly (like the adams). They aren't usually tied to match a specific insect, but rather are a generally attractive fly and can immitate a number of different bugs. The fish might have thought it was an aquatic insect that hatch or even a beetle that fell on the water's surface.
If you want to use dry flies, one approach you could take is to use attractor flies like the ausable wulff, adams, parachute adams, humpy, etc. etc. in a range of sizes between 14 and 18, and search for fish that will take them. Another approach is to use flies tied to immitate specific insects hatching on your river. Talk to a local fly shop or go to google and search for the river and 'hatch chart' or 'fishing report' to see what specific insects might be hatching. Then buy specific fly patterns tied to imitate those specific insects in the sizes listed in the hatch charts or fishing reports.
If you are willing to move beyond dry flies, pick up some nymphs. Again, you can buy some general nymphs like the hare's ear, pheasant tail, and prince nymph, that can pass for a variety of insects or buy ones tied specifically for nymphs that fish might be keying into on your local stream. These will be listed in fishing reports and hatch charts or the fly shop will point you to the right ones. Additionally, if it starts raining you can use small wooly buggers and patterns that imitate worms. Drift the worms in the current and swing the wooly buggers - cast them towards the bank and keep your line tight and they swing below you.
From your post I couldn't tell if you're just getting the bass on the ausable or if you're also going for the trout there. If you are, check out this report
. They list 7 patterns that are working. The first two and last one are dries, the others are nymphs.
I don't have knowledge of the rivers around you. But I thought it would be helpful to talk about the difference between attractor and imitation patterns as well as mentioning that it could help to use some nymphs since trout do most of their eating under the water.