Well, personally, I have never had to do hypo. The last ick I had to deal with was about 12 yrs ago, before we knew about hypo. I am working on a reef tank now, and, when it gets to the stage when I will be stocking fish, I am seriously considering trying out what Terry has resently suggested, and that is QTing fish under hyposaline conditions. I have used a glass hydrometer, which I have tested against other hydrometers and have gotten same readings. I just ordered a pinpoint salinity monitor and will test that out shortly. The monitors are more expensive than most hobby refracts are.
For exacting precision, the refractometer is your best choice, with a quality salinity monitor also being a very good choice for accuracy.
Then a good quality glass hydrometer that reads low specific gravity.