With the acid extraction part of a/b teks I have seen different methods.
Repeated freezing and thawing
Repeated heating and cooling
Long period of soaking at room temperature
Is any method more effective over the others?
Is it worth doing a combination of some/all of the methods?
You missed out sonication and microwaving
They all have their pros and cons depending on your exact goals and specifications, and - yes - it's possible to concatenate some of the methods.
It would probably be helpful to you if you were to look into exactly
why each of the methods might be applied, and what specific action special to each particular kind of extraction technique might be useful to a given situation. For example, freezing helps to break cell walls of plant material so that alkaloids will be released more readily during a subsequent, usually wet, process.
The repeated heating and cooling involves fresh acidic water each time to maximise the amount of alkaloids that dissolve from the plant material.
Room temperature soaks are especially suitable for people who aren't in a special hurry, and have a relative advantage of minimal energy consumption compared to most other methods which possibly makes up for the slowness. Lower extraction temperatures may result in a cleaner initial extract too. In the case of MHRB, this would result in the extraction of far lower quantities of tannins, which would otherwise crash out from a hot brew on cooling, resulting in a slightly inconvenient sludge.
Further details on all these aspects and more can be found throughout the forum and wiki.