The most common method is heating dichloromethane with P2O5, and then distillation.
Have you tried reverse Dean-Stark for azeotropic removal of water. It could work for most of anhydrous reactions.
I never used this method. Usually I have flask with dichloromethane and P2O5 and when I need dry dichloromethane I distilled the desired volume.
Distill from CaH2 works best. I use lump CaH2, reflux for a few hours under nitrogen then distill needed quantity. I typically only use a couple of lumps of CaH2...No need to go overboard with the quan tity if you are using good quality dichloromethane
Molecular sieves are the least work and get it very dry. See: http://pubs.acs.org/doi/pdf/10.1021/jo101589h
Gets it much drier than pretty much anything else, down to 0.1 ppm!
We usually reflux DCM for a few hours over P2O5 and destill it prior use. You can store it after destillation over molecular sieve (5 A) under argon atmosphere for a couple of weeks.
In our labs, we dry DCM simply by placing either Na2SO4 or MgSO4 (of course, anhydrous) inside it . The drying agent will ssettle down & the liquid is either decanted or better distilled (with care).
If You need extra dry DCM. Stirr DCM in P2O5/CaH for 3hrs, distill out the solvent and store over molecular sieves under nitrogen condition
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