I had to repeat the whole process (top and bottom) to really set the starch.
This was partly because while I was doing the bottom, liquid starch was seeping
back into the top, getting it slightly soggy again. You can see here the difference
the second time around the top made:

Here's what it looked like (upside-down) after I was done. (The gathers right
next to the neckband were still damp.):

I let the ruff dry upside-down overnight so that when right-side up, it had
a definite "lift." This caused it to cradle my face in a way that
can be recognized in portraits of the medium-sized ruffs of the 1570s. Here
is what it looked like right-side-up after drying overnight:

Some notes: This process will take two or three hours, and once you start,
you can't stop. Be sure to line your work surface with wax paper or aluminum
foil, and have a wet cloth, a dry cloth, and a bowl of water for continual
de-starching of your fingers. Your iron will get dried and/or scorched starch
on it during the process, but this is easy to clean off with water once the
iron has cooled. If you feel you must do it during the process while the iron
is hot, rub it briskly with a very wet wash cloth, and be careful not to burn
your fingers!
Also, in case you are wondering how in the world you'll know what size figure-eights
to make, here are my methods and revisions. This ruff is actually box pleated
prior to being gathered onto the neckband. It was my theory that this would
provide a guide by which I could make the figure-eights. It did, but it also
hampered the expansion of the ruff, which has to spring almost immediately
from tightly gathered to figure-eight to achieve the look found in period
portraits. The next time I make one, I will simply gather it, but I will mark
it off and tack the edges where the figure-eights will touch in hopes that
this will be a better solution. I think that 16th-century ruffs were not marked
or tacked and owed their form to the expertise of the starchers, but I also
think that I am not yet this accomplished in the art of starching!
Many thanks to Mistress Dorothea van der Zee (Dore') for taking the pictures and being extremely helpful throughout the process!