When I make a cake and cover it with a chocolate sugar glaze (soft ball stage), it seems straightforward to take it off the heat for a few moments and then pour it over the cake to get a beautiful finish. However, I run into difficulty with a chocolate ganache. When I first mix it up, it seems too loose and looks like it will cover too thinly but then when I wait for it to thicken it becomes too stiff and I can't apply it for a nice looking finish - how do I tell when it is the right consistency - is there a certain temperature you can go by ?