You'll do just fine using method B with the dome. It is actually preferable to using the flat disc IMHO. It gives you both an exposure and a ratio quickly and easily.

I go through the so-called "trouble" of using an incident meter to avoid many of the pitfalls of reflective metering, one of which is that reflected meters average things. If I am trying to avoid averaging, why average? The other reason I want to use an incident meter is that reflected meters are subject/composition-based, not light based. If I am trying to avoid composition-based measurements of reflected light by using a hand-held incident meter, why would measuring the light coming from the direction of the camera make sense as a general rule?

There are instances in which I do want an average reading, and in those instances (primarily uncontrolled lighting), I take an averaged reading. But pointing the dome at the camera as a matter of course just makes little sense, even though it is in all the instruction manuals. The dome gives you 180 degrees of coverage to point any way you would like - not just at the camera. Choose where to place those 180 degrees wisely, and you are set.