For Blueberries the Aluminum Sulfate is considered to be a quick fix and and short lived , while a sulfer powder or granule is for the long term and slower.
At least that is what I have been told over the years.

Perhaps some Miracid type product sprayed through a hose onto the foliage may give it a little help as well.
Good luck, .rick.

How did you determine that the problem was pH and iron? For example how did you determine that it was not Mn? How did you determine that the iron would be available and utilized if the pH were adjusted?

You could try mulching with pine straw.

george, there is no lasting solution for this issue. Once someone decides to grow a plant that is not suited to the pH of the surrounding soil, then they pretty much have to attend to that issue for the life of the plant. pH adjustments are NEVER long term. ;-(

Pin Oaks are notorious for this problem, and it could be a frustrating issue for you.

What IS the pH of your soil, by the way? Let's hear how much of a challenge you have.