Well there are two main ways I do single-exposure multigrade printing with a filter set that pivots on a middle gray.
A) Start with low contrast print. Get your overall exposure, then ramp up the contrast to get the whites and blacks appropriate. The advantage here is that you get to see all the information on the negative right away. The disadvantage with this method is that your latitude for the initial exposure on the low contrast filtration is very wide. Therefore, as you ramp up the contrast, your printing time will likely change to some extent (because the exposure latitude at higher contrast filtration is very small).
B) Start with high contrast print and get your overall exposure. Then ramp down the contrast to get detail in the blacks and whites. The advantage here is that you won't have any exposure change as you ramp down the contrast. The disadvantage is that you don't get to see the full information on the negative at the start. Of course it is all there when you look at the negative.