I use Cox Agri Formula B12 + Co as a drench, or I use Brinicombes goat mineral. One or the other, I think if you did both you'd overdo it. I also always have a Red Rockie available.
With the drench, you know they've had it - but you have to drench them
Mine have gone from not touching their food with the Brinicombes powder sprinkled on it, to eating it 'neat'
It has a strong smell, so presumably taste, so seems to take some getting used to.