There are many ways to train and access the subconscious. Musical performance training is one example. I have used alchohol to get some creative brainstorming done. Yoga and Bhuddism have centuries of tradition centered around exploring the subconscious.
People can learn to meditate. Brain scans of people who just learned "fixed point meditation" (where you stare at a dot and tune out your environment) showed up nearly identical to experienced practitioners. The only difference was that the inexperienced people couldn't hold the meditation for very long. But they appeared to be doing it right. [1]
[1] Restak, Richard. "The Naked Brain: How the Emerging Neurosociety is Changing How We Live, Work, and Love." http://www.amazon.com/Naked-Brain-Emerging-Neurosociety-Changing/dp/1400098084
