I coat mine with brushable Loctite glue, Krazy glue also comes in brushable. Tons of people use Sally Hansen's "hard as nails" clear to coat theirs. I just don't like how it takes longer to dry but I do have some.
here is a list of the chironomid coatings I have tried so far over the years -
Sally Hansens
Hard as Hull
Loctite
Krazy glue
regular head cement
one thing though if your using "scud back" material to do bodies then don't use Loctite or Krazy glue as it melts the scud back material and will ruin your fly(s) I either don't put anything on those type of patterns or I use the Sally's
When I do mine I usually like to go half way into the hook bend. gauging your ribbing is done by using wire or whatever material you want for your rib but use the proper thickness. Your only putting a ribbing on to create the body segments of the actual bug, we use different colours more for attractant than actual bug matching.
have a look at some of these
https://www.google.ca/search?q=chironomid&tbm=isch&tbo=u&source=univ&sa=X&ei=i2_nUrulHcGIogTe0IGQAw&sqi=2&ved=0CK8BEIke&biw=1301&bih=544You'll notice that almost every single one in its Pupa stage has 7 distinct ribs/body segments. In its bloodworm stage they can have a lot more segments depending on size of the bug itself