In my experience, no, herbal or alternative therapies do not have much benefit if any at all. Trilostane or lysodren, by far, are the most common and successful therapies at helping to reduce steroid production from the adrenal glands. There are certain conditions where herbal alternatives can be very beneficial but I don't believe so for the treatment of this condition.
If there were any secondary effects on the liver, than a herbal therapy to help support liver function or an antioxidant would be worthwhile, but not specifically for treatment of the Cushing's disease.
Yes, it is possible for a herbal remedy or supplement to interfere with a product like Trilostane. Which ones? No clue because most of the herbal products are poorly understand and their dosing is questionable as well. So, I would be cautious in their use.
Hope that information helps.
FYI: If trilostane for any reason is failing to control Cushing's, that can be common as this medication does not necessarily work in all pets. Under those circumstances and when dose changes have already been done, sometimes, you have to change over to lysodren instead. Important to keep in mind. For me, quite a few pets with some adjustments can do quite well with Trilostane.