For example: I’ve read conflicting things on how to get to one’s darkest darks. Does one start with a series of light washes and slowly build up to darks? Or does one set down one’s darkest dark fairly early, as a benchmark, to help guide the rest of one’s values? (Charles Reid seems to suggest the latter.)

Both methods are used by various artists. Generally, it is easier for most people to work from light to dark. You can always darken a wash with a second application. However, you don’t want to add too many layers, as the wash can then start to get muddy looking. It’s best to put in your darks last, with a good strong value that you won’t have to go over again.
If you have trouble judging the values of the lighter washes, putting some darks in early, can help determine if the light values are strong enough.

Rich

your talent is showing. the face is wonderful, it’s like meeting her, sitting next to her.
you could just lift the chroma in the deepest sleeve shadow, dull down the remaining color and the yellow of the sleeve – sign and sell if you dare part with this.

It looks super! Really, it does. I like the spontaneous feeling you have captured here.
On a side note, I work with watercolors sometimes and have a love and hate relationship with it. It’s really not a forgiving medium at all so I find it easier to work from light to dark since in this way it is easier to “fix” the mistakes than the other way around.