If you can see the wasp nest, you can buy special sprays that will allow you to stand about 10 feet away and shoot at them. Make sure to wear protective clothing and goggles, both for the overspray if the wind moves aginst you, and for some angry wasps. The second photo above shows just how far you can spray with these wasp sprays.
Here is something interesting that I learned while researching this question. In the first photo above the right side is a wasps nest. If it is exposed to the Canadian cold, they will die over the winter and you can simply take it down before the spring. The left side of the photo is not a bees nest at all but a swarm of bees. These bees have broken away from an overpopulated hive. There is no structure here, only a mass of bees swarmed around the queen keeping her protected until a scout comes back to tell them where they are moving to. Don't disturb this group by trying to spray them. Simply cut them loose from the tree and let the whole clump drop into a bucket of water and put a lid on it. They will stay together and all drown.
When bees or wasps have formed a nest inside the protection of your soffits, you will have to get a professional exterminator to come and deal with them because just trying to open the soffits to try and get a shot at them with your store-bought spray will set off a war which you will not win.
Once you have removed flying insects from the soffit area, you need to go back and fill up any small cracks that might let them get back in. Simply stuffing a crack between the soffit and a stone wall with fiberglass will not stop them. You need to use either ridgid mortor, or caulking or foam in a can mixed in with steel wool like cleaning pads, probably made out of brass to be non-rusting.