Hi Jose,
to be honest, didn't look much to the Rainbow, so I cannot advise you much, sorry. Probably like you, I am so busy with my routine duties, that I only do Moodle translations occasionally, sometimes not touching it for weeks. It would be nice use OmegaT somehow to filter the string to be translated or Rainbow or any other free tools, as TRADOS is not cheap.
Good luck with your task!