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Instead of directly farming these another great way to get them is by opening the "Moldy Bags" in the game. These have an extremely good chance of giving you a fine crafting material (a blue one, like this one) and are rather cheap on the Trading Post. Usually ranging from 20 - 50c a bag, depending on the type of bag.

While you won't get rich buying bags, opening them and selling the reagents on the Trading Post you definitely will be able to stock up your collectibles tab at an insanely fast rate. I made a video on how this method works, if you'd like to see it: Fine Crafting Material Farming Video for all skill ranges.

Here are a list of all the bags in the game so you know which type you'll need to buy for whatever item you're after.

Tiny Moldy Bags (0 - 50 Components)

Small Moldy Bags (25 - 100 Components)

Light Moldy Bags (75 - 175 Components)

Moldy Sacks (150 - 250 Components)

Medium Moldy Bags (175 - 300 Components)

Large Moldy Bags (300 - 325 Components)

Heavy Moldy Bags (325 - 400 Components)

Also, Grawls drop these too, they can be found in Grawlenfjord in Wayfarer Foothills roaming around and during an event, and in Plains of Ashford: Martyr's Woods only during an event.

there are also plenty of Sons of Svanir in Outcasts' Cleft in Wayfarer Foothills.

The Bandithaunt Caverns in Queensdale is also a good spot to farm these. They drop from Bag of Pinched Goods, and the pirates respawn very quickly.

If you're looking for an area to farm these, there is a nook right off the main path about mid way through Wayfarer Foothills that has a fairly large amount (10+) Sons of Svanir, and 2 Veteran Sons of Svanir on a short respawn timer. These mobs have a 1/10 chance of dropping them, and you can also get them from the bags dropped from the mobs. There is also two dynamic quests that involve killing the mobs here, so it's a great place to grind. 

Hope this helps.