Most prewar finishes were applied as gloss, but age and conditions can confuse the issues. Others on this site may have more accurate info on the earliest stuff, but I believe Lionel spray painted trains and accessories from the early days into the early 1920's. At some point they started dip-painting. Evidence of this can be seen as drips and runs on the sides of
pea green, peacock, terra cotta and other lead-based colors in that family, up through 1934. In 1935, the color pallet changed to more primary colors and application method changed back to spray-painting, as evidenced by "orange peel" texture seen on these finishes. Again, these colors were applied as gloss, with few exceptions such as silver, or as Lionel called it Aluminum, which was matte. 1940 saw another big change to a more-scale look. Finish colors changed again and were still spray-painted, but many finishes changed to matte, or dull, as noted on some box ends. An exception was car frames which were still dip-painted gloss through most of production. Thick knobs or flakes of thick spots, mainly on frame ends are evidence of this.
