How to clean a glass blunt?
First, push out all the excess materials from the glass blunt (as if you were ashing.) Then we recommend letting your glass blunt sit and soak in a cleaner. We're really big fans of Smoke Soap, by 420 Science, which you can drop your glass blunt into and throw in the microwave for a minute or two. That will really get your blunt clean.
You can let your glass blunt soak in isopropyl alcohol and coarse salt overnight (give it a couple of good shakes so that salt can scrub out some of the grunge and grime.)
There are tons of great cleaners on the market, and some not-so-great ones. Personal opinion, ingredients, and type of residue you are wanting to remove are all factors when selecting the best cleaning solution for your needs.