I don't brew beer (sounds like great fun but I can't start a new hobby). I just read this whole thread to get a better understanding of how to choose and use a pH meter for potted plants.
If it's not too late, I would very strongly recommend that you do NOT use any type of "bedding" soil, top soil, or garden soil in a pot or grow bag. You want to use a soilless medium (although it might be labled as potting "soil" and it will look like what most people think of as soil). Bedding soil, top soil, etc. have absolutely the wrong drainage and water retention characteristics for a potted (or bagged) plant of any sort. They will drown the roots with too much water and too little oxygen, taking too long to dry out between waterings. Even pre-packaged potting "soil" is virtually always far too water retentive and slow draining and, thus, does not allow enough oxygen to the roots for ideal plant growth, but it will do much better than bedding soil.
To keep things simple, I would suggest high quality potting soil such as Pro Mix or Fox Farm. If you want to go a step further, add around 20-40% perlite by volume (depending on how hot and dry your climate is). Even that "recipe" leaves much to be desired, but it will be vastly better in a grow bag than bedding soil.
To answer your question, for plants in containers (pots, bags, etc.) with soilless media, it's typically more useful to pay attention to the pH of your irrigation water/ fertigation solution than the media itself (assuming you start out with a reasonable pH, which the above suggestions will). Controlling the pH of container media can be very difficult, and unnecessary when you irrigate/ fertigate within the correct range. However, if you want to get an idea of the media pH, the best approximation you can get at home is probably with the pour-through method, not by shaking up a sample of the soil/media in water:
www.css.cornell.edu/courses/260/Media%20testing.pdf
Keep in mind that most plants will want to be around a full pH unit lower when grown in containers with soil-less media vs. soil. So, hops like soil at pH 6-7 but in soilless media, they'll do better in the range of 5-6 (FYI, growing in containers is equivalent to hydroponics if you're using soilless media, which includes peat-based "potting soil", so any recommendation for pH in hydroponics would be applicable). On the other hand, if you're planning to grow organically with a living soil, ignore everything I just wrote. However, successfully growing with a living soil in a pot is a far bigger challenge than most people realize. I suggest you stick with "synthetic" fertilizers if you don't have any expertise in organic container gardening.
Finally, keep in mind that the range of pH at which plants take up each essential nutrient varies, so there's no single ideal pH. For example, a plant may take up Mn at pH 5-5.75 but the same plant may take up Ca at 6-7.5, so there's no pH at which it readily takes up both Mn and Ca. The ideal is to let your pH vary throughout the preferred range to ensure the plant will be able to uptake everything it needs.
Hopefully, I will be receiving some hop plants soon that will be planted in 10 gallon grow bags using Kellogg Raised Bedding Soil that has a pH range of 5.8-7.5. I want to measure the pH using my Milwaukee MW102 but I want to make sure if that is advisable.
I plan on taking eight tablespoons of dirt and put it in a beaker. Then I was going to add eight tablespoons of irrigation water and mix it with the soil for a couple of minutes and then let it rest for 15 minutes, then stir again and let the soil settle. Once the soil settles, I was then going take a measurement reading of the liquid only so as not to scratch or damage the probe.
Is my process correct? Will that process damage the probe?
