While using general rules is a good way to help find potential bingos with blanks quickly, sometimes that’s not good enough.  Some positions yield poor results and yield no bingos, while other positions require not just that you find any bingo, but that you find the perfect bingo.  In this case, general rules aren’t good enough: you need to use permutation.

Permutation requires assigning different letters to the blank and trying to figure out whether or not a word exists.

Permuting:
Step 1: Find a baseline. Find a satisfactory play before looking for the best one. Having a default play if you don’t find anything both helps you take the pressure off as well as helps you focus You want a fallback option.

AEHMST?