Very informative guide and so well written. I've earned milions only by attending to my AH hundreds of auctions a few times a week since late Wotlk using AH addons, mainly TSM. This all wouldn't be possible without TSM, originally a very simple addon which then developed into beast which it is now.
Which brings me to my point: you did not mention one powerful feature of TSM - shopping operations. It is them that let me earn millions since they were introduced. First in collaboration with WoWuction, later as a standalone TSM feature.
I don't scan AH with TSM, I don't search for flipping bargains - after all these years I'm too lazy - I let the bargains come to me. TSM shopping operations get me emailed instantly once a bargain appears on AH that meets my criteria (Item sells for minimum 1500g on average and current BO is 15% of item's worth).
I'm not good in writing guides (or even using English for that matter), so perhaps you would feel like to expand your guide to mention shopping operations. Just to show how much potential it has, a recent screenshot of mine below (that day was extraordinarily lucky, it's not that profitable every day, but you get the idea). The items in chat were snatched for few gold/piece via AH phone app after TSM bargains notifications and I expect them to sell for thousands of gold. As you pointed out in your guide, every seller has their own secret strategies, so I'm not revealing my items, but I can say there are plenty of lists of items worth flipping posted all over internet including gold guides here on ownedcore
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I hope you or moderators will not feel like I'm interfering with your guide, if you do - feel free to delete this post. I only meant to share with people something that has been successful for me in WoW consistently for years.
Here's the screenshot.