I don't know of any reliable herd path on Rusk, although there are old roads in the area. What I've always done is to follow the Spruceton Trail (jeep road/horse trail) up to the switchback and then take compass bearing for Rusk. I don't aim directly for the summit, but rather for the ridge a little east, climb to the ridge, then traverse over to the summit. Then you can follow the ridge back over towards Hunter, descend on the Hunter Mt. Trail and head to SW Hunter.
The herd path to SW Hunter is an old rail grade that follows a contour, then you have to climb a little ways up to the summit. I would highly recommend returning to the Devils Path to descend from SW Hunter. Descending down to Diamond Notch off-trail can be rough during leafout season.
No signs on any Catskill peaks except West Kill. About 14 of the trailless peaks have canisters, including Rusk and SW Hunter. Nettles will likely be an issue on the lower parts of Rusk, especially in wet areas. The higher ridges shouldn't be much of a problem, although the aforementioned leafout will make orienteering more difficult than it would be in the winter or late fall.
Matt