I worked in a shop that made FG aircraft parts and we never used an "infusion" layup. We used pre-impregnated(prepreg) fabrics which, in a nutshell, were FG cloth coated with various types of resins. These were then covered with plastic and vacuumed down to make the layup thinner while being "baked" in an oven. Some parts had paper based honeycomb encased in them but otherwise, all the parts were made the same way