Food processor vs food mill

Food mills are inexpensive and an amazing addition to a kitchen. The food processor will not take the 'skins' away.

A food mill will remove the seeds and skin for you, basically straining the jam as you "process" the berries. If you have a China cap or mesh strainer, I would push the berries through it using a laddle after the food processor to remove the skin and seeds.

If you do want the same silky smooth (and seedless!) texture you would get from a food mill, you can pass the blueberries through a fine mesh sieve after having puréed them in the food processor.

You can but you will end up with a more textured jam than if you used a food mill.