Fiber cement siding is very easy to work with, as long as you have the right tools for the job. The cheapest and easiest way to cut the siding is with a handheld circular saw.
The most notable difference between a regular circular saw blade and a fiber cement circular saw blade is the number of teeth. A fiber cement circular saw blade will have very few teeth, which may make you think it will cut slowly. Truth is it will slip through fiber cement boards like a hot knife through warm butter!
This saw blade will cut quickly and easily, but it will kick up a lot of dust! Be sure to wear a mask or respirator while you are cutting. It also helps to work outside and stand upwind to the saw while cutting so all the dust will be carried away from you.