This method works for LIBRAS only if the vocabulary is in the dictionary in either English or Portuguese. The ASL dictionary is very full and makes it easy. The LIBRAS dictionary does not have a lot of basic verbs and nouns (I'm slowly remedying that) but we always need help in adding words and phrases into the dictionary. As an inflected language, all verbs have different endings in Portuguese, so one would have faltar (to lack), but not faltou (I am lacking), faltas (you singular are lacking), faltam (they are lacking), etc., so one has to find a compromise between writing Portuguese and creating an appropriate gloss. Oi (hello) and eu (I) are in the dictionary and alegre (happy or contente) are there, but trying to make a sentence like, "why are you not happy" "porque voce
nao tem alegre" is a challenge.