In TBC I never had any problems getting dusts or essences, I still have my bank alt with a few stacks of Arcane Dust and Cosmic Essences.
However in WotLK I am burning right through all my Infinite Dust from just leveling tailoring alone. I have loads off Dream Shards in my bank for when I get high enough to grab the other recipes but I just can't seem to keep up, I'm not getting any greens at all from doing my Sons of Hodir and Oracle ones and the only place I haven't got the Achievement for is Icecrown.
So how do you keep up your stockpile? It was never an issue in TBC, I got enough greens on the Isle alone to keep more than I needed (hence all on my bank alt) but now I'm stumped. Buying greens on the AH is the only thing I can think of but most of the greens go kinda steep and it seems like it'd be more useful just to buy it directly.
Tailoring is kind of the same, I remember after I made my FSW boots I just needed to farm a few spidersilks and after making a few blues I was there. Now I just have a bunch of crappy epics that are useless to me.
The mats are cheap (cheaper still if you farm them yourself) and the two green level 77 rings yield 2-5 Dust or 1-2 Greater Essences. I couldn't imagine trying to level my Enchanting without Jewelcrafting.
Edit: 'or' not 'and', too busy stuffing chicken in to my face to catch it. :P
I had a similar problem being Tailor/Enchanter and constantly running out of dust. The trick is not to use your own mats for enchants! When I started out, i was coming across loads of greens from leveling so had 100s of dust. I gave away a few free enchants to guildies becuase it helped me level aswell but then ran out and having done all the quests I had no constant supply coming in. At the moment Im sitting on 442 enchanting and have all the recipes except the stam on bracers so im in no rush to get those last 8 skill points. Remember that there isnt a huge rush to get maxed professions since most items arnt that special like they were in TBC.
To restock your supply of dust and essences then Ive found the best place to be Instances. Run the places with lots of trash like UK, nexus etc it surprising how often stuff drops. Granted you have to roll against 4 other people but its still a higher drop rate than just going out and killing random stuff. Im not sure what the price of dust or essences are on your server but a stack of dust sells for anywhere from 120-200g on mine, this is the same price as a single Abyss crystal so you can just run 5 HCs with 4 friends, DE everything and sell your crystal and buy 20 dust, you will also get the drops throughout the instance and it will soon all mount up. The drop rate on normal instances seem to be as high as heroics from what ive seen but they DE into less stuff. e.g 1-2dust from a green in UK normal but 5dust from a green in UK heroic.
if your a tailor just make the low/mid level greens that need a few bolts. its one of those i might have to waste a few bolts to make an item to get the dust to make the cloth i really want. the only reason i would say not to is if x-bolts cost > x-dust cost on ah.