I use hard cast bullets in my reloads, but I don't (yet) cast my own, I'm using store-bought bullets. As such, I don't have a lube recommendation since I use whatever is on the bullets I bought. Chances are, your commercial reloads will be fine as they are - for that matter I don't think you could even add or change the lube on a bullet that's already loaded.
You might talk to the folks over in the Cast Bullet Discussion forum, there are some very knowledgeable posters in there who can likely answer any questions you might have.
Just a Shooter