This is what I use, and it works with both buckets and carboys. I replaced the plastic one a year ago with an extra long stainless baster from a kitchen ware store and it is awesome. But the plastic one from any grocery store works fine.
Here's what I do....
1) With a spray bottle filled with starsan I spray the lid of my bucket, or the mouth of the carboy, including the bung. Then I spray my turkey baster inside and out with sanitize (or dunking it in a container of sanitizer).
2) Open fermenter.
3) Draw Sample
4) fill sample jar (usualy 2-3 turky baster draws
5)Spray bung or lid with sanitizer again
6) Close lid or bung
6) take reading
It is less than 30 seconds from the time the lid is removed until it is closed again.
Probably less if you have help. And unless a bird flies in your place and lets go with some poop, you should be okay.
If you trust your yeast, and don't go by airlock activity, and do like a lot of us do, pitch yeast and come back in a month to bottle, then you really don't need to open your fermenter and take a lot of readings...I take a reading on brewday, and a month later on bottling day I take another to determine ABV...that's for about 90% of my brewing.
BUT...If I am racking to a secondary, or if I have anoy doubts or concerns about my beer, then I take a hydrometer reading...or as many as it takes to tell me what I need to know.
We have a sticky here, Fermentation can take 24 to 72 hrs to show visible signs.
You can wait til it's been 3 days and then take a reading or at least peak inside to see if theres any krausen forming.
But I wouldn't do it any time before that. The yeast may just be lagging which is perfectly normal.