All you have to do is draw your OG sample after adding the yeast and set it next to the carboy with the hydrometer in it. If the hydrometer gets covered with krausen, just pull it out and clean it. Yes, the sample might go weird on you, but it does make it easy to monitor the fermentation. Once the sample reaches the FG, clean everything and draw a new sample.
I've noticed that the sample tube tends to ferment a bit faster than the main carboy, but the FG will be the same.
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