Now that everything scales to your level, I don’t know how to find low-level enchanting mats outside of the auction house.
Furthermore, trying to finish the last 50 points of classic enchanting is infuriating because disenchanting ilvl 60 gear on Kalimdor is giving me TBC enchanting mats.
The best way to “farm” enchanting mats is by using another crafting profession and making armor that will disenchant into what you need. Tailoring is a popular choice as it doesn’t need it’s own gathering profession.
Level 60 BoE greens from Vanilla zones have always DE’d into Vanilla mats for me, even after the changes. What are you trying to DE that’s giving you BC mats? Level 60 epics have often DE’s into BC mats since at least Wrath (and maybe BC.)