AJ, that is one of those maddening things that one never completely
gets control of.....but something of a feeling for it does develop.
The first answer is that it depends on the species, and cubes are again
our friend, and are able to deal with slop on either side of perfect.
So, my answer is spray everything well, very well, until pins pop.
Fan often to keep CO2 down, but do not be afraid of hitting the cakes
directly.
Once I have pins, I will usually wet down the small pile of verm
that I have on top of the cake, but I will try not to mist the young
fruits directly. At that point you want to spray the perlite and the
sides and inside-lid of the box.
The perlite should keep the RH good, for the most part.
Grit your teeth and be patient. This should only take a few days
to a week.
Good luck,
JD