Render first, then export. But you did use a rather render intensive plugin. And 3.5 hours of it...it might take a while. I applied a plugin called NEAT Noise Reduction. And only to about 30 min of a 51 min doc. Render time was 15 hours.
Speed it up? Faster processors are key....More RAM might help a little. If it is a plugin that utilizes GPU, a better graphics card might help a lot too.
Shane
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