This is how i do
Go to ippc.no create a briefing for my route.
Check the surface wheather looking for cloudbase
Check SWC chart for icing
Ofcourse you need to look up the freezinglevel but as i am operating in Sweden that is usually below surface (this winter is an exception though).
IF i have deicing (fiki or not, My experience with non fiki tks system is very good) as long as the base is high enough and the tops low enough i dont worry too much since i know i have a way out...
If the above criteria is not met i go to wheatheronline.co.uk expert charts and try to figure out if there are layers i can navigate so to stay clear of ice.
Even though i have FIKI (pa46 Mirage) i dont want to be stuck in icing, always find a layer or go on top!