Do it right or don't waste your time, especialy since the access is difficult. Tear out the current soffits and remove the underlying restrictive wood. Make sure your attic insulation isn't impacting the air flow and install baffles to make that happen. Then reinstall vented soffit for the whole eave area. However, a vented soffit works in conjunction with a ridge vent for your roof, so that needs to be installed as well. Cutting more holes will NOT help at all. Everything works as a system.

Or the alternative is to make the roof the sealed plane and to create an unvented attic. That will take some $$ in spray foam insulation however and is less DIYable because of that.

The soffits in the first link appear to have vents. If you have those, the next thing is to remove one of them (you can probably pry it out gently), then peek behind to see if there might be solid wood blocking the venting. That's what I found on our house, i.e. that it was installed more as a cosmetic thing than properly. Once I discovered that, I temporarily removed the vent trim, bored sufficient holes (every 6 inches I think), installed round vents, then reinstalled the existing vents.

Also make f=certain you havr either a ridge vent or the correct amount of roof vents as without these no amount of soffit vents will work properly