Originally Posted by wtfDean
also, breezy is right. the refractometer is only useful before there's alcohol in the beer.
I'd disagree a bit, if the reading is stable it will tell you if fermentation is complete without needing to take 2 full samples. I've also found Sean Terrill's refractometer calculator to be quite accurate with all but very highly attenuated beers (I'm usually double checking with a hydrometer myself but not always on a small batch).
When using a bucket for primary I actually just leave the lids a bit loose because I have such trouble getting them off even with a wrench. I haven't had any infection or oxidation issues, although the beers aren't in there more than about 2wks, maybe 3wk tops if dryhopping.