"Traditional bonsai practices" isn't really a category. Those "Traditions" have seen a revolution in the last 100 years and especially in the last 20. The introduction of decent metal tools, and especially cheap, available copper wire in the early 20th century changed old ways to allow drastic changes to be made to trees. In the last 20 years, things have gone even further, with the use of electric reciprocating saws and concrete rebar ushering even more capabilities to make extreme bends and trunk reshaping. Modern pesticides and fertilizers have also allowed more advanced growing practices to take hold.
Some of the current practices used by Japanese bonsai professionals are far from the "zen" stereotype typically associated with bonsai by those who haven't been doing it a while.
There are no "traditional" bonsai practices, in the sense you're after. They aren't some group of romantic, ancient ritualized secrets performed by "masters". They are practical and get specific jobs done and typically employed by groups of poorly-paid (and increasingly Western) apprentices at most of the notable bonsai nurseries. For instance, in competitions, it's not uncommon in Japan for professionals to glue fruit on living trees in the best areas on that tree. Show trees are also treated like stable horses, spruced up for shows--given temporary ancient pots to live in for a couple of months, have a lush moss carpet laid down on the soil surface for a month, etc. After the show, they're put back in their old pots, etc.
The esthetics behind bonsai may be more what you want to read about. Those haven't really changed. Learn especially about the esthetics and practices in the formal Japanese Tea Ceremony. Practitioners of the tea ceremony had a huge guiding influence on current bonsai esthetics and display.
Wabi Sabi,
Shubui and
Yugen are all underlying principles of bonsai.
And avoid anything that says "bonsai is zen." That's a shallow, uninformed explanation that Westerners buy into about bonsai. Also avoid feng shui, also shallow crap ;-)