I don't think they even used prober dictionairies to look up words. When checking the greek texts with an interlinear translation and Koine-dictionairy, many expressions and words in the NWT seems to be grabbed from classical Greek, modern Greek or just by pure insertion or homemade invention..
An example of this is the translation of "kolasis".
Gr. "kolasis" means punishment, torment or punishment by torment.
The NWT translates this "cutting-off".
That means that the passage in Matt. 25:46 does not say:
" And these will depart into everlasting cutting-off, but the righteous ones into everlasting life.”"
but rather
"And these will depart into eternal punishment by [torment], but the righteous ones into everlasting life.”"
http://www.forananswer.org/Matthew/Mt25_46.htm
The reason for doing this is obvious: They wished to change the passages in the bible to support their own doctrine which denies Hell as a Christian teaching, so that when JW's read the bible, they would find "biblical evidence" that supported their own belief. So they went fishing for expressions and justifications for them in various dictionairies and other bible translations.