I don't know what the temp was down in MEL, but did anyone think to use some tap water, the temp of the tap water will be higher than ambient, and should melt the ice/frost without a problem,
EK's A340-500's get ice/frost on the upper wing surface regularly, the engineers in SYD just hose it off with the potable water hose.
It's not hard, water in pipe warmer than ambient and ice/frost = melt
As long as ambient is above freezing! duh