Cake flour differs from All-Purpose flour in several ways. It has a lower protein content which makes it more tender. It also has more starch, which gives a finer texture, and is chlorinated, which helps fat stick to it (I love Alton Brown!). So I don't think sifting AP would give you the same result. Don't worry, using AP probably won't ruin your recipe, but it won't be quite the result you would get from cake flour.
Cake flour I have found is sold in boxes as SoftaSilk or Swan's Down (not packaged like regular flour). Good luck!
Quote by @%username% on %date%
%body%