Leonard, I`d go along with Ghenghis, S-p and Twochai;I spent several winters in Canada doing helicopter icing trials between `69-75`,using the facilities at NRC in Ottawa,and home facilities such as `blower `tunnels,cold chambers ,etc,. As said ,things have moved on with better facilities etc.Before venturing into IMC for real icing we waited for a good stable airmass to give `fairly` uniform moisture content at reasonable `helicopter` altitudes,to build-up confidence in the instrumentation,the aircraft systems, Air Traffic (who thought we were `nuts`),and the crew,particularly if you ended up losing an engine,or the ice would`nt shed off.I know helos are `different`,but such trials are not taken lightly,either F/W or Rotary,so one also needs a good range of diversions as well.
You could also consider the use of an airborne `tanker`,for those early days,blue skies, which can also give you excellent info on water droplet size,flow rates,etc. As stated ,don`t go looking for Cbs,you`ll end up with tears....
Google `aircraft icing tankers..`