When I discover I'm blister-prone in some location, I start taping that location on both feet (or hands or whatever) with Leukotape P. I put it on the night before the race with foot bent or extended to allow maximum movement because the tape isn't stretchy - just extremely sticky. It seems to stick better if you put it on in advance. In Ontario, you can get it at Shoppers Drug Mart Home Health Care stores (not regular Shoppers stores). Trav and Baloney taught me about it.
When it's too late and I already have a blister, it can help to use Second Skin on top of the blister with really good adhesive tape (like Leukotape) holding it in place. It will still hurt but the Second Skin is not sticky and it's like stiff Jello so the friction from your shoe is not fully transferred to the painful area. I checked and it appears to be available in Finland.
Another option is to cut the shape of your blister out of the Leukotape (or other adhesive tape) and cut another larger piece of tape. Stick the sticky sides together and tape your blister with only the unsticky side of the tape touching your blister. That doesn't put any padding over your blister, which can be better or worse depending on where it is and how much pressure there is against your shoe.
Take your shoes off whenever you can to help the blister to dry out faster.
The expert on this is John Vonhof, who wrote the book "Fixing Your Feet" and also has a website. He has all kinds of ideas that might work better for you. Feet are very individual.
Hope it clears up soon!