Below about 20, the engine oil gets to be pretty stiff, so hand cranking it up to speed is a real chore. If you have electricity, a magnetic oil pan heater on the lower case to loosen up the oil and warm up around the mains would be a big help. If you don't have power, and can get under the case, a alcohol stove under the case for a little while would probably work wonders on a cold start...
On the top end, I pour a little alcohol in around the injector and light it to preheat the injector and upper HP fuel line. This aids in that first cold startup.