My Japanese is limited. I first learned from books (mostly to read the tags & catalogs that came with my Godzilla and Ultraman toys), but they provided very little information I needed.
To freshen up my basic Japanese, I took the language in my last year of high school. The Japanese teachers were surprised about my knowledge of tokusatsu, and one of them liked the Ultra Series (Mrs. Nagano drew a little picture of Ultra Mother on a note she sent me)! and another even told me what the names of the Gorangers were, since I was into Super Sentai, and hadn't heard of
Goranger beyond the title (in
Markalite #1) and a few pictures! This was a year before we got the Internet, so it wasn't as luxurious as we have it today.
I have a friend who, for over a decade, has been a great tutor for me. He is a big tokusatsu and anime fan, and I credit him for everything. He told me what the different terms were, how to read certain things in Japanese, what traps to look out for (some words have different pronunciations to them; for example, the character for "Big Dipper," 斗, can be read as another character for "fight" - "tataka(u)"), and many other things. He has really pushed me hard enough to improve myself as I go along.