As one of our roles in the Perrine joint project is to do translation checks, I would like to take some time to describe how I personally do translation checks. As for everything that is done in fansubbing, how I do it is potentially different from how other folks would do the same task.
One of the things you probably noticed from our recruiting efforts is that we do not try to recruit someone who specifically does translation checks. The reason is very simple; it is my opinion that a translation checker must be able to be a translator as well. There is no point in being a checker when you do not know the language well enough to translate it, as lacking proficiency in the language that is being translated will cause gross translation errors to be missed.
My mindset when it comes to translation checks is almost exactly the same as translating an episode. The only difference is that I do not have to type out the translation if the translation is similar enough to how I would translate it. For this reason alone, translation checking goes considerably faster than translating. However, in all other aspects, I am still literally translating an episode. I am merely not typing out my entire translation.
A lot of my translation is by instinct, and the same thing goes for doing a translation check. If a translation does not feel right, I will investigate the lines in question in detail until the translation is satisfactory. Therefore, unless if the translation is completely correct, it usually will take me about a couple of hours to do a translation check. Compared to three or four hours for a typical translation (since I have to type it out), it definitely goes a lot faster.
For this reason, any series I do a translation check requires the same amount of background research and preparation as any series I translate. It is the best way to ensure a good translation. On the flip side, as a translator, I appreciate having someone check my work. I am not a perfect translator, and I do make mistakes. With another set of eyes looking over my work, it ensures that everyone will benefit from a good translation when they watch the episode.