I haven’t looked at the video but I’m guessing they show a sample container that will stand on a work top with the hydrometer floating inside? A sample container like this will take quit a bit of beer to fill to the float level. I use the plastic shipping tube the hydrometer came in. Takes less beer to float the hydrometer. You do need to hold it in your hand to make sure the hydrometer is floating freely but doing that doesn’t involve a lot of time.
I don’t take an original gravity sample for extract brews. The OG will be as stated in the recipe if you use all the extract and your volume is correct as @hd4mark has said . Quite often I will only take one FG sample. This is for beers that are not high gravity and have been in the primary for at least three weeks with nothing out of the ordinary happening during the fermentation. These one sample beers have also been brewed multiple times with the same yeast.
