French to English Bus/Financial Materials (Plastics, Ceramics, etc.)

This is the sentence:

Il a effectué des travaux d'isolation en tant que applicateur de ouate de cellulose et il a assuré la pose de film régulateur vapeur, en vue d'obtenir l’étanchéité a l'air sur un ensemble de bâtiment a structure bois.

I do not understand the technicalities of this job description very well and am very unsure what the correct translation would be. 'Applicateur' seems in most cases to refer to an instrument rather than person, but in this sentence, it seems that it refers to the person himself (title of his job).

I would greatly appreciate your help!