"I was wondering if the herbal bowel balance formula should be used after a proper bowel cleanse or if there are any preliminaries to do before"
From my experience, if Herbal Bowel Balance formula (LBB) is available to you, get some as this in and of itself will constitute a significant bowell cleansing program, both short term (perhaps as a preliminary to the prep flushes) and long term. I plan on using LBB regularly either for the rest of my life or for as long as I am able to purchase it.
Preliminaries? There are lots of them: proper daily intake of pure water; improve your daily diet; remove common household toxins/cleaners from your house; stop using toothpaste; stop drinking coffee; stop drinking pop; stop eating moldy foods (breads, cereals) and pre-packaged processed foods. These may require life-changing measures to change habits, temporarily turning your world upside down in the process, so it comes down to the question of how many of these will you be willing to integrate into your life?
I did the standard Clark liver flush last year for the first time, and used all Clark methods and products for all of the prep flushes before hand - parasite, bowell and kidney. (exception - I got parsley locally for doign the parsley tea routine). I prepared for nearly 6 months (the dental cleanup took me about 3 months). The first flush went pretty well, no problems, no surprises.
After too much delay, I'm now preparing for the second liver flush, but this time I am going to try some different products for the prep flushes. As far as I know, MH's kidney cleanse formula contains all of the Clark-suggested kidney cleanse ingredients plus some extras. This should be fine as a total replacement to the Clark kidney cleanse.
As to the amalgam question, Clark states in her books "for best results, dental cleanup should be done prior to a liver flush". As easy as it is to suggest this, doing it is not so easy for various reasons. MH is also a big advocate of dental cleanup. The liver flush is geared towards detoxing the body. Mercury is a common toxin in the body. It makes less sense to detox if you still have sources (amalgams) of mercury in your body. If you don't get rid of the amalgams, this probably does not preclude you from doing a liver flush, but....... you probably won't get best results. In any case, do what you feel you can do. Good luck!