We tried that Lean approach at my last company (market & media research), and it was a total waste of time, not to mention the "expert" was running a racket. He'd written several books (OK, maybe 2 or 3) on the topic and was considered a guru of sorts, but - this was market research - every project (product) was custom. The guy we hired assured us that Lean could be adapted to our business model, and he got paid, and in the end everyone agreed it was a waste of money. It applies well if you have a finite number of items / options - even if it's 6,000 variations when you're building a car and take into consideration the trim, drive train, interior / exterior colors, options etc - it's still a finite number. Our variations were infinite and were dictated by the customer.
If you're trying to apply Lean or whatever to flipping on eBay, I suppose the best you can do is set up your listing templates, set up your photo area and camera settings, set aside a dedicated pack & ship area that has flow, and utilize the USPS options for free packaging / discounts / pick-up. Over & above that, you'll still have to treat every item as unique in some way. I'm far from lean nor do I have any flow, nor do I want to - that's more like work - and at any moment I can see myself saying "fuck it" and donating everything to a GW the next time I get infuriated with an eBay buyer.