Do not use pitch on the collective or pedals to slow the blades down –droop stops depend on friction for proper operation, and all you will be doing is lightening the load where it ought not to be.

Icing
Ice adversely affects performance, not only by adding weight, but also altering the shape of lift producing surfaces, which changes your stalling speed – autorotation could therefore be a lot more interesting than normal (the US Army found that half an inch on the leading edge reduces your lifting capacity by up to 50%, and increases drag by the same amount) – if your engine stops, you could really fall out of the sky!
On top of that, fuel could freeze in wing tanks, as could control surfaces, and slush picked up on take-off could stop the landing gear from operating, as well as flight instruments.
Zero degrees is actually the point at which water becomes supercooled and capable of freezing. Airframe icing happens when supercooled water droplets strike an airframe below that. Some of the droplet freezes on impact, releasing latent heat and warming the remainder which then flows back, turning into clear ice, which can gather without noticeable vibration. On the ground this can mean ground resonance, and bits of ice flying off rotor blades. In flight, the extra weight and drag could cause descent and improper operation of flying controls. So—it's a good idea to avoid icing conditions but, in any case, you shouldn't go if you haven't got the equipment, which naturally must be serviceable. The "clean aircraft concept" means that nothing should be on the outside that should not be there, except, perhaps, for deicing fluid.

All ice should be removed from critical areas before take-off, including hoar frost on the fuselage, because even a bad paint job will increase drag, which is relevant if you're heavy, and hoar frost will have a similar effect. Deicing details should be entered in the relevant part of the Tech Log, including start/end times, etc. The critical areas include control surfaces, rotors, stabilisers and the like.
The ability of an object to accumulate ice is known as its catch efficiency; a sharp-edged object is better at it than a blunt-edged one, due to its lesser deflection of air. Speed is also a factor. Due to the speed and geometry of a helicopter's main rotor blades, their catch efficiency is greater than that of the fuselage, so ice on the outside of the cabin doesn't relate to what you might have on the blades. In fact, Canadian Armed Forces tests show that you can pick up a lethal load of ice on a Kiowa (206) rotor blade inside 1-6 minutes, although it’s true to say that 206 blades, being fairly crude, don’t catch as much as more sophisticated ones, such as those found on the 407. It’s also true that some helicopters, such as the Sikorsky S61, will not take ice on the main or tail rotor blades down to about –1 Centigrade, due to friction.