If you have been watching cake boss, then you may have heard them say that they use a mix of fondant and modelling chocolate for some of their cakes. They have said that they mix equal weights of the two.
White modelling chocolate can be made at home the same way as other kinds of modelling chocolate but you have to use real white chocolate http://en.wikipedia.org/wiki/White_chocolate
and not candymelts/coating.
and you can use "ounces" 30 ounces chocolate + 9 ounces by weight corn syrup
You may also find it easy to just use the white modelling chocolate by itself, if you work in a coolish room 65F with chilled crumb-coated cake.