If you use ther Sephra fountain you would pre heat the fountain on 8 for 1/2 hour or so and then add the chocolate, turn it down to 4 to run it.
It is 1-2 cups oil to 10 lbs of white chocolate, pre melt it on a low double boiler first. 10 lbs is the minimum amount to run the big fountain.
If the chocolate is too thick then you heated it up too much.
i've found the cheaper chocolates work better, say Belcolade or Peter's vs. Cluizel.
Have fun cleaning it when you are done