Hello Allen
Well, I think checking for varroa as you described it with a mesh
over a board is not suited for untrained personal as you mentioned to
use. When you insert this from the front of the hive you will bother
the bees and may receive a sting if you are in a hurry. If you have a
mesh floor you go to the colony from  the back side and the drawer
were you can count the mites is completely isolated from the bees by
the mesh. Here mite counting can be done by any untrained people even
without protective clothing because you dont get in contact with the
bees. Also treatments that work with fumes can be placed on this
drawer without any contact to the bees.
I have some (old) hives with a closed floor wich I diagnose and treat
in a similar way as you described and also have some mesh floors.
Need at least double the time for the closed floor and not fun. I
understand that the prize is a top argument for a professional as
you, if you already have closed floors. I make these floors my self
and think that they are relatve simple, should not cost more than the
closed ones. So for replacement they are a good option.
 I found a diagram of Imhoff et al about the natural mite fall in
October over the varroa population in a colony (test of 90 colonies).
With 1 mite per day the average was 500 mites in the colony, but the
minimum was 200 and the maximum 1000. The spread is quite big, but
for the decision to treat or not this method is precise enough.
Wolfgang
 
 
 
Wolfgang Poehlmann, Hobby Beekeeper in South Germany
Email: [log in to unmask]
homepage: http://home.t-online.de/home/wolfgang.poehlmann/imkerei.htm