Welcome to the Nexus!
The fact that many of the teks don`t use accurate measurements but rather estimates is not necessarily because of the writer`s lack of skills, but rather it`s a sign about how extractions are actually very `forgiving`.
As an example, say we want to explain to you how to make a cheese toast. Sure we could measure the exact amount of cheese, but we could also just say `cover the bread with cheese`. If you put some more or some less cheese, it won`t matter too much, given you are within reasonable parameters (but I can understand how for a new person this might seem a bit confusing since hey haven`t realized this quite large `maneuver margin`).
As another example, say you want to add lye/NaOH to a solution to raise the pH. Someone might say "dissolve 50g lye in 1 liter water", which would turn the pH to around 14, and it would be good for an A/B. But if a person adds half that amount, the pH is still 13.8, which is definitely still high enough. Or someone might say add 100g of lye, which would be very high, 14+, so while it is not strictly necessary, it would help reducing any chances of emulsions. So if someone would say `add 25g lye` or `add 50g lye` or `add 100g' lye or 'add around 5 full tablespoons of lye`, it would all be just as correct and easy to follow and work as well.
By the way, emulsions are exactly the `3rd layer` you are talking about, they are no mistery. Emulsions are caused by suspended microdropplets from the water layer that dont separate from the top non-polar layer. This happens commonly and it can easily be prevented and dealt with, as explained in our FAQ. Emulsions are usually created by shaking, and not high enough pH. You are probably familiar with emulsions in cooking, for example mayonese is a big persistent emulsion of an acqueous part (for example the egg), together with an oil, which are mixed at high speed.
Goopy results are not necessarily related to emulsions, they are more likely to be either the presence of NMT from acacia confusa (which tends to be `stubborn` and refuse to crystallize, though infusing some herbs is a fine way to deal with that), or they can also be due to remaining solvent trapped together with the alkaloids, so if you keep scraping and re-scrapping the oil tends to crystallize/harden up.
Lastly, keep posting in these areas, askign questions and answering questions, participating in the threads you can post in, and very soon im sure you`ll be promoted to full membership.
Be well!