You've missed Rare Skipper for the season, I think -- it's univoltine with a peak in June with the first buttonbush bloom. Aaron's has a second (but smaller) brood which should be about mid-way now.
I've never had much success on the Refuge itself, but have found them most often between Vienna and the Refuge -- sometimes in good numbers -- on any second flush buttonbush or clethra along Decoursey Bridge Road (especially at the landing) and New Bridge Road, again centered around the landing. Much depends on how the county has been mowing; I haven't been down that way since early July.