Lay them out on a paper towel overnight so that the skins dry completely. This gives the benefit of keeping the frozen blueberries from sticking together without needing lots of freezer space to do a quick freeze individually on a sheet pan. Then bag in a freezer bag and freeze.
Note that whenever you freeze fruit, the liquid will burst the cell walls as it thaws, causing the resulting berry to be mushier. In my experience, frozen blueberries aren't good for eating alone. To bake with blueberries, thaw them by placing them in a mesh sieve or collander and running water over them until the water is clear off the bottom (no pigmentation from the skins, which may color your baked goods) and the berries are thawed. Dry the skins before using in baking.
Using these techniques I have not once had any of the 30 pounds of blueberries I froze this summer burst in the freezer and have successfully made many blueberry baked goods from the results.
Common names of plants are a very unclear matter. There are big differences not only between languages, but also regional differences within a single language.
There are lots of (closely related) plants which are sold under the name blueberry. And probably not even the person who grew (or gathered) them can tell you the exact species. While it does matter when it comes to jam (for the same reason it matters whether you use Roma tomatoes or Cherry tomatoes for a sauce) it is highly improbable to find a source which can consistently provide you with a specific known variety. Also, you probably have to study some very specified botanical literature and be provided with parts of the plant other than the berries in order to be able to identify the type with some degree of accuracy.
On the other hand, don't let that come in the way of good jam. Blood orange marmelade may taste different than bitter orange marmelade, but both are good. The same goes for blueberries: you can use any variety, even if some of them would be a bit better on their own.
What you need for a jam is a good sweetness to acid ratio, the proper amount of pectin, and as much aroma as possible. A softer texture also helps to prevent unpleasant lumps. So generally, you want to go with the ripest fruit available. They are soft, and have the fullest aroma. This is something you might want to consider with your current source of berries: maybe they're not a special "green on the inside" variety, but only underripe. If they don't taste very sweet, and their aroma isn't very complex, I'd try to find other sources. Farmer's markets and organic stores are usually able to sell much better fruits (because they cater to a picky, price-inelastic clientelle), but of course they cost a lot too.
Sweet fruit is always good, but you need enough sugar added for food safety. A ratio of 2:1 (fruit to sugar) can still be kept in the pantry, more fruit than that and you need to refrigerate the unopened glasses too. With blueburries, you'll need to add both pectin (to get the jam to gel) and acid (to get the pectin to work). This is the part which will vary with fruit variety: more watery types will need more pectin, and less acidic types will need more acid. If you want a good quality jam, you'll need to do some experiments until you get the proportions right. If not, you can buy "jam sugar" or however it is called in your country - this is sugar with pectin and acid already added. It won't have the perfect ratio for your fruit, but it will more or less work. But then, if this quality is enough for you, you can skip buying the expensive berries and slaving at the stove, and buy manufactured jam.
Best Answer
While you could probably do dried blueberries in a VERY low oven (150F), you'll most likely need to prop the door open slightly to allow moisture to escape. You'd be best to do them in an actual food dehydrator which will have a fan to expell the moisture being released from the food.
Keep in mind however that if dried as they are, they will shrivel up into fairly hard little bits. If your goal is something similar to the dried blueberries that you can buy in retail stores, they will have to be treated in a sugar syrup to maintain the chewy texture and keep them from totally drying out. I'm not sure if the commercial producers are first drying and then soaking in a sugar solution and perhaps drying again so that the sugar is drawn into the cells of the berry. Whatever the case...commercial dried cranberries and blueberries maintain the chewy texture due to being treated with a sugar solution at some point.
If you are looking for ways to handle a bumper crop or bulk buy on blueberries, I would recommend freezing them and stick to buying commercially processed dried berries for the best results, least effort, and greatest bang for your buck.