How much revision is done varies enormously from unit to unit. There are units where every single translation is revised. There are others where the resources to do this are not available. In these cases, the criteria used to decide what texts will be revised include the importance of the text itself, its length, whether it has been translated by a newly appointed translator, and so on. Some units try to send to freelances only texts where no quality control is required, in order to avoid having to revise freelance translations. Others try to revise all freelance work. Still others do not have the resources to revise all of it, and are obliged to rely on spot checks.
Policy varies as well about who will do the revision. In some units, revision is seen as part of an hierarchical structure, where a senior person revises the work of a more junior person. In others, revision is seen as team work: two translators sitting together on the grounds that four eyes see more than two.
The tools used by revisers are the same as those used by translators, except that a reviser will not normally dictate his modifications to the translation. He will either hand-write the corrections on the paper version or work directly on the electronic version. Otherwise he will make use of all the tools and resources for documentation and research that the translator himself uses. Indeed, there is a sense in which a reviser's need for quick and efficient access to documentation is even greater than that of the translator, in that the variety of different texts that the reviser may deal with in any given period of time is greater than that dealt with by the translator.