I've never seen much value in trying use preset hunts. There just seems to be too many variables. As you know Randy Anderson's method of calling (usually) involves what he calls the 3 stages. 1, coyote vocals, 2 prey distress, 3 pup/coyote distress. It is a good overall pattern, but not without exceptions. If you see coyotes in the field or have reason to think they are close, then going right into prey distress works well without howls.
The main purpose of the howl is to notify coyotes that another coyote is in the area. Hence howls that have names like Invitation howl, Lonely howl, Long howl. Sometimes that's all it takes and here they come. This time of year, when mating is getting into full swing, they are looking either for a mate or to defend territory where they will den. That makes them very susceptible to howls. They still have to eat, so prey distress also works, but in heavily called areas they've heard about all the rabbit sounds they want to hear. I've seen them hightail it out of Dodge at the first sound of prey distress. (Using sounds they probably haven't heard as much will work sometimes).
Finally there are the various coyote distress sounds and fight sounds that may bring in otherwise hung up coyotes. From breeding season (now) right on up through whelping and rearing pups (June/July) they will be more tuned to sounds that seems like a pup is in some type of distress and needs help.
There is no substitute for just going, listening, and learning. No matter whether you hear coyotes howl or not, they will respond to howls. Just don't overdo it. Two or three howls to say I'm here will usually be sufficient. If they howl back, I tend to Challenge howl back at them if they sound aggravated or angry (sharper ending on their howls mixed with barks).