Dan Tan has put together a noteworthy series of posts comparing the NDP's actual position on trade to its portrayal in the media, then discussing the effect of the gap between the two on party members. But while Dan seems to show some sympathy for an attempt to cultivate a difference between media portrayals and actual policy, I'll suggest the NDP's goal should instead be to make sure that its real position is known and promoted to the greatest extent possible.
Of course, it will help to keep the party's policy book accessible and ensure easier access to the NDP's trade policy on its website. But the root of the current problem of perception seems has plenty to do with the fact that even people with a strong connection to the party are looking to the media for guidance about its positions - meaning that sending different messages through different channels won't particularly help other than with a narrow group of people who are monitoring the website religiously without looking at what MPs are saying about the topic at hand.
And indeed, any attempt to finesse the corporate media is almost sure to be too cute by half. There's no feasible means of sending a distinct message to supporters which will completely escape the media's notice - so while the stenography pool might be happy to eat up whatever message the NDP chooses to send in one-off interviews, the corporate apologists in the media will only find fodder to question the party's beliefs. And the only way to deal with the resulting questioning is to have a strong answer.
(Not to mention that a future NDP government could face far more pushback in actually giving effect to the party's values if those pushing the "NDP=Libs!" line blame the party for their own failures when the government tries to implement its agenda.)
With that in mind, the NDP should use the media exposure available to the Official Opposition as directly as possible in promoting the party's actual values - including the reason why they differ from those of the Libs and Cons. And when progressive Canadians hear the message that free trade is just one possible tool which carries significant risks and downsides (rather than the be-all and end-all as believed by the other parties) from the NDP through all available channels, that will ensure that everybody with an affinity for the NDP's views knows exactly which party to support.