Thank you! I see you are in Canada. Blueberry loves organic matter. You can add lots of organic matter in the planting hole. Organic matter is naturally acidic. If you can get your hands on peat moss, it would be helpful to add in the planting hole. Peat moss itself is quite acidic. You can also use sulfur, but I would use very little. Sulfur has fungicidal properties and can negatively affect soil biology if overused. (I personally don't use sulfur). If you have pine trees around you, you can mulch your blueberry bushes with pine needles. Coniferous mulches have a PH in the 3.5 - 4.5 range). Hope this helps.
I purchased my comfrey from Coe's Comfrey. Not sure if you can receive plants shipped from the U.S. You can purchase root cuttings and start the plants yourself or purchase comfrey crowns that will grow bigger and faster than root cuttings.
I have been using quite a lot of comfrey fertilizer this year on all my annual vegetables. I have never harvested so many squash from my food forest before. I highly recommend making your own comfrey fertilizer. It is a gardener's best friend! I am here and love to help other people grow food organically. If you have any questions, please don't hesitate to ask. I am always happy to help if I have the knowledge.