I don't know how it helps. But personally I would not use any drugs just to attempt lucid dreaming. Even if it's proven that smoking marijuana would give a big percentage that you'll have a lucid dream, I would not. Heck, even if lucid dreaming could only happen if you do drugs(although we all know it does not), I would just forget lucid dreaming and live a drug free life.

A site telling facts about marijuana: http://www.acde.org/common/Marijana.htm